How to Hire a Backend Developer (ASP.NET)

Q: You have developed a custom middleware for logging requests in your ASP.NET Core app. What is the easiest way to add this middleware into the HTTP request pipeline?

Correct answer: Use app.UseMiddleware () in Program.cs. Using app.UseMiddleware () is the standard and simplest way to register custom middleware in ASP.NET Core, ensuring it becomes part of the request pipeline.

Q: In an ASP.NET Core application, you need to implement custom middleware that logs the duration of each HTTP request for performance analysis. Where should this middleware ideally be placed in the request pipeline?

Correct answer: At the very beginning of the pipeline to capture the entire request duration. Placing the middleware at the beginning ensures that the entire processing time—from the moment a request enters until the response is sent—is captured, providing a true measure of performance.

Q: When deploying an ASP.NET Core application within a microservices architecture, which communication approach most effectively balances performance with security for inter-service calls in a production environment?

Correct answer: Implement gRPC over HTTP/2 with mutual TLS. gRPC leverages HTTP/2 for performance and supports streaming, while mutual TLS provides robust security for service-to-service communication in microservices deployments.

Q: Walk me through what happens to an HTTP request from the moment Kestrel receives it until your controller action's return value is written to the client as JSON.

Why it matters: Separates candidates who understand the middleware pipeline, routing, and model binding from those who treat ASP.NET Core as a black box that calls their controller. What to listen for: Green flags: Kestrel accepts the connection and creates an HttpContext; the request flows through middleware in registration order (exception handler, HTTPS redirection, static files, routing, authentication, authorization); endpoint routing selects the action; model binding pulls values from route, query, and body; [ApiController] returns an automatic 400 if ModelState is invalid; the result is serialized by System.Text.Json; and the response travels back out through the middleware in reverse. Red flags: 'IIS handles it', no idea why middleware order matters, or confusing middleware with MVC filters.

Q: Tell me about the most serious production incident you handled in an ASP.NET Core API. How did you find the root cause, and what did you change afterwards?

Why it matters: Mid-level engineers are expected to own APIs operationally, not just write code. What to listen for: Green flags: concrete signals (Application Insights failure rates and dependency durations, dotnet-counters thread-pool queue length, SQL Server wait stats, App Service SNAT port metrics), a mitigation such as scaling out or toggling a feature flag followed by a durable fix (async all the way, IHttpClientFactory, an index), and a blameless post-mortem with action items. Red flags: blaming others, no data, or a 'fix' that only restarted the App Service.

Q: Tell me about the most significant architectural decision you drove on an ASP.NET Core platform. What alternatives did you reject, and how did it play out?

Why it matters: Seniors are hired for judgment; the quality of their trade-off reasoning matters more than the outcome itself. What to listen for: Green flags: explicit alternatives with criteria (consistency, latency, Azure cost, operational load, team skills) — e.g., App Service vs Container Apps vs AKS, or gRPC vs REST vs Service Bus for an integration — a written ADR, measurable results, and honest discussion of what they would change. Red flags: resume-driven choices ('microservices on AKS because it's modern') or no measurement of outcomes.

Q: During development, you notice that a required service is not being injected into your controller. What is the most likely practical reason for this issue?

Correct answer: The service was never registered in the dependency injection container. A common real-world error is neglecting to register a service in the DI container, which results in the controller not receiving the necessary dependency.

Q: When registering a DbContext for an ASP.NET Core application, which service lifetime is most appropriate to avoid threading issues while ensuring efficient database operations?

Correct answer: Scoped, to create one instance per HTTP request. DbContext is not thread-safe and should be scoped per HTTP request to ensure that it is used safely and efficiently within the context of a single request.

Q: In a high-traffic ASP.NET Core application that handles large file uploads, which strategy is most practical to minimize memory usage and improve performance?

Correct answer: Stream file uploads directly to storage using asynchronous I/O. Streaming uploads directly to storage with asynchronous I/O minimizes memory footprint and efficiently handles large files under heavy load.

Q: Tell me about a bug in one of your .NET projects that took you more than a day to solve. How did you eventually find it?

Why it matters: Juniors will regularly be stuck; how they investigate and when they escalate determines how much senior time they consume. What to listen for: Green flags: reading the full exception including InnerException and the first frame in their own code, using the Developer Exception Page and breakpoints, enabling EF Core SQL logging to see the generated query, reproducing the bug with a failing xUnit test, and asking for help with a clear summary of what they already tried. Red flags: random code changes until it works, wrapping everything in empty try/catch blocks, or never asking for help.

Hiring Workflow, Step by Step

Every stage of this hire can run in SkillSauce on one board, from the first applicant to the offer. The level sections below add the detail for junior (0-3 years), mid-level (3-6 years) and senior (6+ years) hires.

1
Open a Job Profile for the role
Create a Job Profile for the role: one Kanban board, free on every plan, that holds every candidate, test and interview for this hire. Write the job description with the free Job Description Generator, or start from the template in your level below.
2
Fill the candidate pool
Publish the job on your Career Page and share the link on LinkedIn, X and job boards, so every applicant lands on the board. To reach people who have not applied, search Candidate Lookup by domain and seniority, then narrow by industry, company and location. You can also import LinkedIn profiles by URL, upload resumes in bulk or import a CSV.
3
Shortlist the strongest resumes
Move applicants into the Resume Shortlister: TESSA AI scores every resume against the Job Profile and shows its reasoning, so you can see why each candidate made the cut before you send a single test.
4
Test the skills the role needs
Send the shortlist an IT assessment on C# 12 / .NET 8+, ASP.NET Core Web API and Entity Framework Core + SQL Server, with a coding test in any of 60+ languages. Build it from the Question Library of 320,000+ questions, or let TESSA AI generate it when your exact skill mix is missing, and keep AI proctoring on for remote candidates.
5
Interview with TESSA AI
Invite the candidates who pass to a TESSA AI interview on the role itself, in any of 100+ languages. Add a Culture Fit round to see how they work with a team like yours, and a Behavioural round for senior hires, where judgment and ownership matter most.
6
Meet the shortlist
Schedule the live technical round on Zoom or Google Meet with Google Calendar invites, and keep candidates posted on WhatsApp or email.
7
Decide together and make the offer
Compare finalists on their Reports: scored results for each test and AI interview, plus the proctoring activity of proctored tests. Collect your hiring team’s feedback on each candidate, then make the offer with the email templates in your level below.

Company Fit: Startups, SMBs and Enterprises

Startups

Startups choose ASP.NET Core when they want a fast, strongly typed backend with first-class Azure integration and generous startup credits through Microsoft for Startups. SkillSauce helps founders hire ASP.NET Core engineers who can go from dotnet new webapi to a secured, observable API on Azure App Service in days, without burning founder time on manual technical screens.

30–45 minute ASP.NET Core practical assessments that verify candidates can ship a validated, tested minimal API or controller endpoint with EF Core from a fresh template.
TESSA AI interviews that screen for ownership and speed, so founders only spend live interview time on the strongest .NET applicants.
Assessment scenarios built around MVP realities: JWT bearer or Entra External ID authentication, EF Core migrations, and one-click deployment to Azure App Service or Container Apps.
Start free: the Starter plan includes 40 credits, about 10 AI interviews or assessments, with no time limit and no card needed.

SMBs

Growing companies typically run a handful of ASP.NET Core APIs that have started to strain: EF Core queries that were fine at 10,000 rows, lifetime bugs that only appear under concurrency, ad-hoc caching, and authorization rules scattered across controllers.

Performance-focused assessments that objectively measure EF Core N+1 elimination, captive-dependency fixes, output caching, and policy-based authorization through automated SQL-count and test grading.
Standardized scoring rubrics so every hiring manager evaluates ASP.NET Core candidates the same way.
TESSA AI interviews that check production ownership: incident response on Azure, API versioning, and code review habits.
Turnkey onboarding signals: assessment reports highlight each hire's strengths and gaps to shape their first 90-day plan.

Enterprises

Enterprises and regulated industries (banking, insurance, healthcare, government) run large ASP.NET Core estates on Azure — often alongside legacy .NET Framework applications mid-migration — where security, consistency, and auditability are non-negotiable. SkillSauce gives them a globally consistent, defensible way to benchmark ASP.NET Core architects and engineers across regions, business units, and delivery partners.

Architecture-grade senior assessments covering the transactional outbox on Azure Service Bus, multi-instance correctness (Data Protection, SignalR, distributed caching), resilience handlers, and Entra ID security with chaos-tested grading.
Audit-ready evaluation trails with timestamped scoring, rubric versions, and proctoring evidence for compliance and fair-hiring reviews.
Consistent global benchmarking for in-house teams and Microsoft partner or outsourcing vendors, using the same ASP.NET Core rubric in every geography.
Custom assessment libraries aligned to internal platform standards such as shared ServiceDefaults packages, API design guidelines, and secure-by-default authentication baselines.
Evidence in one place: scored reports for every test and AI interview, with your hiring team’s feedback beside them.

Junior level

Junior Backend Developer (ASP.NET)

Experience: 0 - 3 Years
Average time to hire: 10 - 18 Days

Core tech stack

C# 12 / .NET 8+
ASP.NET Core Web API (controllers & minimal APIs)
Middleware pipeline & built-in dependency injection
Entity Framework Core + SQL Server
xUnit & WebApplicationFactory
OpenAPI / Swagger UI

How to Hire a Junior Backend Developer (ASP.NET)

Hiring a junior ASP.NET Core developer is about confirming they understand the request pipeline the framework builds for them, rather than pasting Program.cs snippets from tutorials. At 0–3 years, look for solid C# fundamentals (async/await, LINQ, records, nullable reference types) applied inside ASP.NET Core: a working mental model of the middleware pipeline and why registration order matters, registering services in the built-in container with a deliberate choice between AddTransient, AddScoped, and AddSingleton, building a controller or minimal API endpoint with DTOs and [ApiController] validation that returns proper status codes and ProblemDetails, persisting data with EF Core migrations against SQL Server, and proving it works with xUnit and WebApplicationFactory. Being able to read an 'Unable to resolve service for type' exception and fix it in two minutes matters far more than reciting the MVC lifecycle diagram.

1
Define a Realistic Junior Scope
Write down the slice of the codebase a junior will own in their first quarter: CRUD endpoints in an existing ASP.NET Core Web API, EF Core entities and migrations against SQL Server, DataAnnotations or FluentValidation rules on request DTOs, and xUnit tests. Explicitly keep Kestrel tuning, AKS deployments, Microsoft Entra ID app registrations, and SignalR scale-out off the junior's plate so the ad does not scare away strong graduates.
2
Source From .NET Learning Communities
Target graduates and bootcamp alumni who have completed Microsoft Learn's ASP.NET Core learning paths and then built something of their own: a fork of the dotnet/eShop reference app with new features, a JWT-secured todo API using minimal APIs and route groups, or a Blazor front end backed by a Web API. Microsoft Learn Student Ambassadors, r/dotnet, and local .NET user groups surface learners who have actually run dotnet ef database update against a real database. Beyond applicants, Candidate Lookup finds people by domain and seniority, narrowed by industry, company and location, and you can add them to the same pipeline.
3
Screen With a 30-Minute SkillSauce Practical Assessment
Send a SkillSauce task built on a pre-generated dotnet new webapi project: add GET and POST endpoints for an Order resource, map it with EF Core, register the service with an appropriate lifetime, return 201 with a Location header on success, 400 ValidationProblemDetails on invalid input, and 404 for unknown IDs, and make the provided WebApplicationFactory tests pass. Auto-graded dotnet test runs remove reviewer bias and immediately filter out candidates who cannot build and run a .NET solution. Build it in IT Assessments from the Question Library, add a coding test in the language you hire for, and keep AI proctoring on.
4
Run a 15-Minute TESSA AI Interview
Use TESSA to check communication and learning habits: how the candidate would approach a Developer Exception Page showing an InvalidOperationException from the DI container, how they ask for help after being stuck for half an hour, and how they explain dependency injection to a teammate who has never written C#. TESSA runs this AI interview in any of 100+ languages and returns a scored report you can share with the team.
5
Hold a 45-Minute Pair-Debugging Session
Hand the candidate a broken ASP.NET Core API: an IOrderService that was never registered in Program.cs, app.UseAuthorization() called before app.UseAuthentication() so every [Authorize] endpoint returns 401 even with a valid token, an EF Core entity returned directly from a controller that throws 'A possible object cycle was detected' during System.Text.Json serialization, and a .Result call on an async repository method. Observe how they read the exception and inner exception, use breakpoints, and verify each fix with a test.
6
Extend an Offer With a Mentorship Plan
Close within 10–18 days with a written 90-day plan, a named senior .NET mentor, and an explicit learning budget (a Microsoft certification voucher such as AZ-900, plus course subscriptions such as Pluralsight or Dometrain). Junior .NET candidates frequently hold offers from Microsoft partners and IT services firms, so speed and a visible growth path win.

Pro Tips

Give them eight middleware calls (UseExceptionHandler, UseHttpsRedirection, UseStaticFiles, UseRouting, UseCors, UseAuthentication, UseAuthorization, MapControllers) on cards and ask them to order them. Then ask what breaks if UseAuthorization runs before UseAuthentication. Candidates who see the pipeline as an ordered chain of delegates answer instantly; tutorial copy-pasters guess.
Ask why AddDbContext registers the DbContext as scoped and what would happen if it were injected into a singleton caching service. Strong juniors define transient (new per resolution), scoped (one per HTTP request), and singleton (one per application) and may mention the 'Cannot consume scoped service from singleton' error the container raises in Development.
Probe serialization habits: returning EF Core entities with navigation properties either throws 'A possible object cycle was detected' or silently leaks columns such as PasswordHash. Look for DTOs or records and LINQ Select projections instead of ReferenceHandler.IgnoreCycles as a band-aid.
Show a controller that calls _orders.GetAllAsync().Result and ask what is wrong. Good answers mention 'async all the way', passing the CancellationToken from the action (or HttpContext.RequestAborted) into EF Core's ToListAsync, and that blocking calls tie up thread-pool threads under load even though ASP.NET Core has no SynchronizationContext deadlock.

Junior Backend Developer (ASP.NET) Job Description Template

Use this template to attract early-career C# engineers who have built at least one ASP.NET Core Web API and are ready to ship production endpoints under close mentorship.

Junior Backend Developer (ASP.NET) Job Description

Role Overview

We are hiring a Junior Backend Developer (ASP.NET) to join our API team building REST services on ASP.NET Core and .NET 8+. You will ship well-tested endpoints in an existing Web API, persist data with Entity Framework Core and SQL Server, and learn production practices — environment-specific configuration, health checks, structured logging, and CI/CD to Azure App Service — from senior engineers who review every pull request.

First 90 Days Deliverables

Days 1–30: Run the API locally with dotnet watch and a SQL Server container from Docker Compose, apply migrations with dotnet ef database update, explore the endpoints through Swagger UI, and close 3–5 starter tickets such as adding a validated property to a request DTO ([Required], [StringLength]), fixing an endpoint that returns 200 with a null body instead of 404, or documenting response types with [ProducesResponseType] so they appear correctly in the OpenAPI document.
Days 31–60: Deliver a complete CRUD feature — a controller or a minimal API route group created with MapGroup, a service registered in the DI container with the right lifetime, an EF Core entity configured with IEntityTypeConfiguration<T>, and a reviewed migration — plus xUnit unit tests (Moq or NSubstitute) and WebApplicationFactory integration tests with 80%+ line coverage on the new code.
Days 61–90: Add an IExceptionHandler that maps a domain exception to a ProblemDetails response, expose a /health endpoint with an EF Core DbContext health check, bind a new settings section to a strongly typed options class via IOptions<T> with appsettings.Staging.json overrides, and deploy the feature to the Azure App Service staging slot through the GitHub Actions pipeline.

Must-Have Requirements

Solid C# fundamentals: classes, interfaces, generics, LINQ, async/await, records, and nullable reference types.
Hands-on experience building at least one ASP.NET Core Web API using controllers or minimal APIs, including routing, model binding, and correct HTTP status codes.
Understanding of the built-in dependency injection container and the difference between transient, scoped, and singleton lifetimes.
Entity Framework Core basics: DbContext, DbSet, relationships, and code-first migrations against SQL Server.
T-SQL basics: joins, primary and foreign keys, and simple indexes.
Comfort with the dotnet CLI, NuGet packages, xUnit or NUnit, Git branching, and pull request reviews.

Nice-to-Have Skills

JWT bearer authentication or ASP.NET Core Identity basics.
FluentValidation, Serilog, or AutoMapper/Mapster in a real project.
Docker and Docker Compose for local SQL Server and Redis.
Azure fundamentals (AZ-900) or experience deploying to Azure App Service.
Debugging fluency in Visual Studio, JetBrains Rider, or VS Code with C# Dev Kit.

Benefits & Mentorship

Dedicated senior ASP.NET Core mentor with weekly 1:1s and pairing sessions.
Learning and certification budget (Microsoft certification vouchers, books, and course subscriptions).
Competitive junior salary, health coverage, and a documented promotion rubric to Mid-Level within 18–24 months.

Need a version for another role or tone? Draft one with the free Job Description Generator.

Sourcing Channels for Early-Career ASP.NET Core Talent

Junior ASP.NET Core developers congregate where Microsoft's ecosystem teaches and showcases .NET: Microsoft Learn programs, the official reference applications on GitHub, and beginner-friendly .NET communities and user groups.

SkillSauce

Candidate Lookup

Find people who have not applied yet. Search by domain and seniority, narrow by industry, company and location, and add them to the role’s Job Profile with their available contact details.

SkillSauce

Career Page and LinkedIn Import

Publish the job on your Career Page and share the link on LinkedIn, X and job boards: every applicant lands in the role’s Job Profile. Import a LinkedIn profile by its URL when you spot someone.

Social network

X (Twitter) (opens in a new tab)

x.com

Post the role with hashtags such as #dotnet and #aspnetcore, and join the X Communities where people in the field share their work.

Student Program

Microsoft Learn Student Ambassadors (opens in a new tab)

studentambassadors.microsoft.com

Microsoft's global student program whose members run workshops on .NET, Azure, and ASP.NET Core at their universities. Ambassadors who have demoed a Web API or published a Learn module walkthrough are self-driven juniors with public evidence of communication skills.

Open Source Directory

GitHub dotnet/eShop Forks (opens in a new tab)

github.com

eShop is Microsoft's reference ASP.NET Core application (minimal APIs, EF Core, .NET Aspire). Review forks with meaningful commits — a new catalog endpoint, extra integration tests, a different database provider — to find juniors who went beyond cloning the sample.

Social Community

r/dotnet Subreddit (opens in a new tab)

reddit.com

Active Reddit community where early-career C# developers post portfolio APIs, ask about EF Core migrations and DI lifetimes, and share learning plans. Engage with well-written project showcases and lead with your mentorship program rather than cold-spamming.

Developer Community

.NET User Groups on Meetup (opens in a new tab)

meetup.com

The .NET Foundation's Meetup network lists hundreds of local .NET user groups. Junior attendees who present lightning talks or help at hands-on ASP.NET Core workshops are strong candidates; sponsoring a meetup puts your mentorship story in front of them directly.

Recruitment Platform

LinkedIn Boolean Search – Early-Career ASP.NET Core Talent (opens in a new tab)

linkedin.com

Use: ('ASP.NET Core' OR '.NET Core' OR 'Web API') AND ('C#') AND ('Entity Framework' OR 'EF Core') AND ('SQL Server') AND ('Graduate' OR 'Junior' OR 'Associate' OR 'Intern'). Filter for 0–3 years and recent CS or bootcamp graduates; exclude profiles that mention only WebForms or Classic ASP.

Developer community

Stack Overflow (opens in a new tab)

stackoverflow.com

Find people who answer questions in the tags your stack uses: their answers show how they reason and explain.

Job boards

Job Boards

Post the job on Indeed and Glassdoor, and on Naukri and foundit for hiring in India. Where a board allows it, use your Career Page link as the apply link, so applicants land in the same Job Profile.

Campus and referrals

Campus Placement Cells and Referrals

Partner with college placement cells and career services for graduates and interns, and ask your team who they studied or interned with.

Early-career .NET developers respond to outreach that promises real tickets in a modern ASP.NET Core codebase, genuine mentorship, and a fair practical evaluation instead of whiteboard puzzles.

LinkedIn Post

We're hiring a Junior Backend Developer (ASP.NET)! Built your first ASP.NET Core Web API and want to see how one runs in production? Join our API team and ship real endpoints from week one — with a senior .NET mentor reviewing every PR. Stack: C# 12, ASP.NET Core on .NET 8+, EF Core, SQL Server, xUnit, Azure App Service What you'll learn: middleware and DI done right, EF Core migrations, WebApplicationFactory integration tests, CI/CD to Azure Support: weekly 1:1s, certification budget, a clear promotion path No whiteboard puzzles. Start with a 30-minute hands-on SkillSauce challenge: [SkillSauce Assessment Link] #dotnet #aspnetcore #csharp #JuniorDeveloper #BackendDeveloper #Hiring

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Twitter / X Post

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Shipped an ASP.NET Core Web API for your portfolio? We're hiring a Junior Backend Dev (C# + ASP.NET Core + EF Core + SQL Server). Real tickets, real mentorship, real code reviews. Show us in 30 mins, no LeetCode: [SkillSauce Assessment Link] #dotnet #aspnetcore #DevJobs

LinkedIn Direct Message

Hi [Candidate Name], I came across your [ASP.NET Core project / GitHub repo name] — nice work separating DTOs from your EF Core entities and adding integration tests, which most portfolio APIs skip. We're hiring a Junior Backend Developer at [Company Name] to build REST endpoints on ASP.NET Core and SQL Server, paired with a senior .NET mentor from day one. Instead of a CV screen, we use a short 30-minute SkillSauce practical where you add a validated endpoint to a small Web API: [SkillSauce Assessment Link] Would you be up for giving it a try, or for a quick 15-minute chat first? Best, [Your Name]

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Email Sequence for Junior ASP.NET Core Candidates

A short, encouraging sequence that tells junior .NET candidates exactly what they will build, how they will be evaluated, and the support they will get once they join.

Cold Sourcing

Subject: Junior ASP.NET Core Developer role at [Company Name] — mentorship from day one

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Hi [Candidate Name], I saw your work on [Project/Repository] and liked how you kept business logic in a service class registered through dependency injection instead of stuffing everything into the controller. At [Company Name] we're growing our .NET API team and are hiring a Junior Backend Developer (ASP.NET). You'd build REST endpoints on ASP.NET Core and SQL Server, write tests with xUnit and WebApplicationFactory, and deploy to Azure within your first 90 days — with a senior engineer mentoring you throughout. Our process starts with a practical 30-minute SkillSauce exercise (add a validated endpoint to a small Web API and make the tests pass) rather than algorithm puzzles: [SkillSauce Assessment Link] Would you be open to a short call this week? Best regards, [Your Name] [Your Title], [Company Name]

Interview Invite

Subject: Next steps: Junior Backend Developer (ASP.NET) at [Company Name]

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Hi [Candidate Name], Thanks for your interest in the Junior Backend Developer (ASP.NET) role! Our next stage has two short parts you can complete on your own schedule within the next 4 business days: 1. SkillSauce Practical Assessment (30 mins): You'll receive an ASP.NET Core Web API project with EF Core already configured. Add GET and POST endpoints for an Order resource, register your service in Program.cs, return the correct status codes (201, 400, 404), and make the WebApplicationFactory tests pass: [SkillSauce Assessment Link] 2. TESSA AI Interview (15 mins): A conversational interview about how you learn, how you debug, and how you work with code review feedback: [TESSA Interview Link] Tip: use Visual Studio, Rider, or VS Code — whatever you're comfortable with — and run dotnet test before submitting. Once our team reviews your results, we'll schedule a friendly 45-minute pair-debugging session with one of our senior engineers. Good luck! [Your Name] [Company Name]

Offer Letter

Subject: Offer of Employment: Junior Backend Developer (ASP.NET) at [Company Name]

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Dear [Candidate Name], We're delighted to offer you the position of Junior Backend Developer (ASP.NET) at [Company Name]! Your SkillSauce submission stood out for its clean DTO mapping and complete integration tests, and our engineers enjoyed tracking down the middleware-ordering bug with you in the pairing session. Offer Summary: • Position: Junior Backend Developer (ASP.NET) • Base Salary: [Salary Amount] per annum • Equity / Bonus: [Equity or Bonus Details] • Start Date: [Start Date] • Reporting To: [Engineering Manager Name] • Mentor: [Senior Engineer Name], Senior .NET Engineer • Learning Budget: [Amount] per year, including a Microsoft certification voucher (e.g., AZ-900) and course subscriptions • Equipment: Laptop with 32 GB RAM, Visual Studio Professional or JetBrains Rider license, and a home-office stipend • Benefits: Health, dental, and vision coverage, [PTO Days] days paid time off, and retirement matching Please sign and return the attached agreement by [Offer Expiration Date]. We can't wait to see your first pull request merged! Warm regards, [Your Name] [Company Name]

Junior ASP.NET Core SkillSauce & TESSA Assessment Blueprint

A two-part evaluation that confirms the candidate can build and test a real ASP.NET Core endpoint end to end, then measures the coachability and communication that drive junior ramp-up speed.

30 mins

SkillSauce Junior ASP.NET Core Web API & EF Core Assessment

Candidates receive an ASP.NET Core Web API solution with an EF Core DbContext and an xUnit test project. They must implement POST /api/orders and GET /api/orders/{id}, register an IOrderService implementation in Program.cs, return 201 with a Location header via CreatedAtAction or TypedResults.Created, return 400 ValidationProblemDetails for invalid payloads, return 404 for unknown IDs, and pass a hidden WebApplicationFactory test suite. Graders also check that async EF Core methods are awaited (no .Result), the CancellationToken is passed through, and EF Core entities are not exposed directly in responses.

Focus:: Controller or minimal API routing, model binding and [ApiController] validation, DI registration and lifetimes, EF Core persistence, correct status codes, and WebApplicationFactory testing.

15 mins

TESSA AI Learning Agility & Communication Interview

TESSA runs an adaptive conversational interview asking the candidate how they would investigate an API that throws 'Unable to resolve service for type' on the first request, how they incorporate reviewer feedback, and what they learned from their last ASP.NET Core project. Responses are scored for clarity, honesty about gaps, and a structured troubleshooting approach. TESSA AI runs it as a Behavioural round and returns a scored report for the hiring team.

Focus:: Explaining dependency injection and the middleware pipeline, structured debugging, responding to code review, and asking for help.

Why This Assessment Mix

Junior ASP.NET Core hires rarely fail on C# syntax; they fail on the framework: services never registered in the container, middleware added in the wrong order, entities serialized straight from controllers, blocking .Result calls, and untested endpoints. The 30-minute SkillSauce task exercises exactly these first-quarter tickets inside a real ASP.NET Core host with automated WebApplicationFactory grading, while TESSA measures the coachability and communication that determine how quickly a junior becomes independent. Together they predict ramp-up speed far better than resume keywords like '.NET' or 'MVC'.

You can run tests like these in SkillSauce: build an IT skills assessment from the test library and turn on AI proctoring for remote candidates.

Behavioral & Fundamentals Rubric for Junior ASP.NET Core Developers

Use these questions in the live session to check how well the candidate understands the framework, how they debug, and how they learn from feedback.

Walk me through what happens to an HTTP request from the moment Kestrel receives it until your controller action's return value is written to the client as JSON.

Why it matters: Separates candidates who understand the middleware pipeline, routing, and model binding from those who treat ASP.NET Core as a black box that calls their controller.
What to listen for: Green flags: Kestrel accepts the connection and creates an HttpContext; the request flows through middleware in registration order (exception handler, HTTPS redirection, static files, routing, authentication, authorization); endpoint routing selects the action; model binding pulls values from route, query, and body; [ApiController] returns an automatic 400 if ModelState is invalid; the result is serialized by System.Text.Json; and the response travels back out through the middleware in reverse. Red flags: 'IIS handles it', no idea why middleware order matters, or confusing middleware with MVC filters.

Tell me about a bug in one of your .NET projects that took you more than a day to solve. How did you eventually find it?

Why it matters: Juniors will regularly be stuck; how they investigate and when they escalate determines how much senior time they consume.
What to listen for: Green flags: reading the full exception including InnerException and the first frame in their own code, using the Developer Exception Page and breakpoints, enabling EF Core SQL logging to see the generated query, reproducing the bug with a failing xUnit test, and asking for help with a clear summary of what they already tried. Red flags: random code changes until it works, wrapping everything in empty try/catch blocks, or never asking for help.

When would you register a service with AddTransient, AddScoped, or AddSingleton? Give a real example of each from something you built.

Why it matters: Lifetime mistakes are the most common source of subtle ASP.NET Core bugs, and this question shows whether the candidate made deliberate choices or copied registrations.
What to listen for: Green flags: DbContext and repositories as scoped (one per request), lightweight stateless helpers as transient, thread-safe shared state such as a configuration cache or IMemoryCache wrapper as singleton, and awareness that a singleton must never hold a scoped DbContext. Red flags: 'I register everything as singleton for performance' or no idea what scoped means.

Describe a time you received critical feedback on your code in a pull request. What did you change?

Why it matters: Code review is the primary learning channel for juniors joining an ASP.NET Core codebase with established conventions.
What to listen for: Green flags: a specific example (e.g., moving business logic from a controller into a service, replacing synchronous EF Core calls with async versions, or returning DTOs instead of entities), understanding the reason behind the feedback, and applying it in later PRs. Red flags: defensiveness or a vague, generic answer.

TESSA, the SkillSauce AI interviewer, can run a structured first-round interview built around questions like these. See how TESSA AI interviews work.

Verified Junior ASP.NET Core Technical Questions

Five EASY-tier multiple-choice questions taken verbatim from the SkillSauce ASP.NET Core question bank (it/question_bank/ASP.NET Core.json), covering custom middleware registration, DI container registration, built-in logging, URL-based API versioning, and first-step performance troubleshooting.

You have developed a custom middleware for logging requests in your ASP.NET Core app. What is the easiest way to add this middleware into the HTTP request pipeline?

Easy

aPlace the middleware class in a dedicated folder and let it auto-register
bUse app.RunMiddleware<CustomMiddleware>() in Startup.cs
cConfigure the middleware in appsettings.json
dUse app.UseMiddleware<CustomMiddleware>() in Program.csCorrect

Explanation: Using app.UseMiddleware<T>() is the standard and simplest way to register custom middleware in ASP.NET Core, ensuring it becomes part of the request pipeline.

Why it matters: Checks that the candidate knows how custom middleware joins the pipeline in a modern WebApplication-based Program.cs (not the legacy Startup.Configure). Follow up by asking what the middleware class needs (a constructor taking RequestDelegate and an InvokeAsync(HttpContext) method), the difference between app.Use (calls next), app.Run (terminal), and app.Map (branches), and where in the order a request-logging middleware should sit. Note that RunMiddleware in option b does not exist.

During development, you notice that a required service is not being injected into your controller. What is the most likely practical reason for this issue?

Easy

aThe service was injected using constructor injection rather than property injection
bThe service is being manually instantiated in the controller
cThe service was never registered in the dependency injection containerCorrect
dThe service interface was registered with a transient lifetime but should use singleton

Explanation: A common real-world error is neglecting to register a service in the DI container, which results in the controller not receiving the necessary dependency.

Why it matters: Targets the single most common junior error in ASP.NET Core: 'InvalidOperationException: Unable to resolve service for type IOrderService while attempting to activate OrdersController'. Follow up by asking them to write the fix (builder.Services.AddScoped<IOrderService, OrderService>()) and justify the lifetime. Option a is backwards — the built-in container only supports constructor injection — which makes it a useful probe of whether they know that.

When setting up an ASP.NET Core application for production, which method should you use to efficiently capture and log errors?

Easy

aInsert multiple Console.WriteLine() statements throughout your code
bRely solely on try-catch blocks without a logging system
cConfigure logging providers in Program.cs using the built-in logging frameworkCorrect
dUse a custom logging method without integrating it into ASP.NET Core

Explanation: ASP.NET Core's built-in logging providers can be easily configured to log errors and other events, which is a best practice for production environments.

Why it matters: Assesses whether the candidate uses the Microsoft.Extensions.Logging abstraction correctly: injecting ILogger<T>, writing structured message templates (_logger.LogError(ex, 'Order {OrderId} failed', orderId) rather than string interpolation), and controlling verbosity through the Logging:LogLevel section in appsettings.json. Follow up on how unhandled exceptions reach the logs via UseExceptionHandler and AddProblemDetails, and on providers such as Serilog or Application Insights.

You're building a versioned API using ASP.NET Core. What is the recommended way to handle API versioning in the URL structure?

Easy

aOmit versioning entirely to keep URLs simple
bCreate separate projects for each API version
cUse query string parameters exclusively for versioning
dEmbed the version number in the URL routes (e.g., /api/v1/resource)Correct

Explanation: Embedding the API version in the URL is a common and straightforward method for versioning APIs in ASP.NET Core, making it easier for clients to target the correct version.

Why it matters: Tests basic awareness of API contract evolution. URL-segment versioning (/api/v{version:apiVersion}/orders with the Asp.Versioning.Mvc or Asp.Versioning.Http packages) is the easiest scheme for a junior to reason about and test. Treat 'recommended' as convention rather than a framework rule: follow up by asking what header or query-string versioning would look like and why you would never maintain a separate project per version.

An ASP.NET Core application is experiencing sporadic slow response times. As a first step in your troubleshooting process, what practical measure should you take?

Easy

aRemove middleware components without analysis
bUse the built-in logging to monitor and track request processing timesCorrect
cAssume the database is causing the issue and focus solely on it
dImmediately refactor all middleware components

Explanation: Monitoring request processing times via built-in logging is a practical and efficient way to diagnose performance bottlenecks within the middleware pipeline.

Why it matters: Checks the 'measure before you change' instinct. Strong juniors mention the request-finished log lines from the Microsoft.AspNetCore.Hosting category (which include elapsed milliseconds), app.UseHttpLogging(), EF Core command logs that show each query's execution time, and Application Insights request telemetry — then narrowing the slow path down before touching any code.

Need more questions for this stack? Browse sample questions by skill in the SkillSauce Question Library.

Constructive Rejection Templates for Junior ASP.NET Core Candidates

Junior candidates remember how they were treated, and the .NET community is tightly networked through user groups and Discord servers. Give specific, learnable feedback and point to official resources so your employer brand grows even when you say no.

Post-Assessment Rejection

Subject: Your application for Junior Backend Developer (ASP.NET) at [Company Name]

Show template

Hi [Candidate Name], Thank you for taking the time to complete our SkillSauce ASP.NET Core assessment. We know a hands-on exercise takes real effort, and we appreciate it. After reviewing your SkillSauce report, we've decided not to move forward at this stage. The hidden test suite showed gaps in a few areas that are central to this role — specifically [e.g., returning ValidationProblemDetails with a 400 status / registering services in the DI container / awaiting EF Core calls instead of using .Result]. These are very learnable: the ASP.NET Core Web API tutorials on Microsoft Learn (learn.microsoft.com/aspnet/core) are an excellent next step. We'd genuinely welcome a new application in 6 months as you build more ASP.NET Core experience. Best of luck with your search! Kind regards, [Your Name] [Company Name]

Post-Interview Rejection

Subject: Thank you for interviewing with [Company Name]

Show template

Hi [Candidate Name], Thank you for spending time with our team during the pair-debugging session. [Interviewer Name] particularly appreciated [specific positive, e.g., how methodically you read the inner exception to find the unregistered service]. After careful consideration, we've decided to proceed with another candidate whose experience more closely matches our current needs. This was a close decision. If helpful, our feedback is that strengthening your understanding of [e.g., middleware ordering and how authentication and authorization interact] would make you an even stronger candidate. We'd be glad to keep your profile on file for future junior openings and hope our paths cross again. Warm regards, [Your Name] [Company Name]

Mid-Level level

Mid-Level Backend Developer (ASP.NET)

Experience: 3 - 6 Years
Average time to hire: 18 - 25 Days

Core tech stack

ASP.NET Core 8+ (filters, endpoint filters, ProblemDetails)
EF Core (AsNoTracking, split queries, migration bundles)
SQL Server / Azure SQL Database
JWT bearer auth & Microsoft Entra ID (Microsoft.Identity.Web)
Output caching & Redis (IDistributedCache / HybridCache)
Rate limiting middleware & IHttpClientFactory resilience
xUnit + WebApplicationFactory + Testcontainers
Azure App Service, Key Vault & Application Insights

How to Hire a Mid-Level Backend Developer (ASP.NET)

Mid-level ASP.NET Core engineers (3–6 years) own APIs end to end in production. The bar moves from 'can build an endpoint' to 'can keep an API fast, secure, and observable under real load': choosing between middleware, MVC filters, and minimal API endpoint filters; spotting captive dependencies where a singleton holds a scoped DbContext; using the IOptions, IOptionsSnapshot, and IOptionsMonitor variants deliberately; diagnosing EF Core N+1 queries and cartesian explosions with AsNoTracking projections and AsSplitQuery; writing authorization policies over Entra ID scopes and app roles; caching with output caching and tag-based eviction; protecting public endpoints with the rate limiting middleware; and proving it all with WebApplicationFactory and Testcontainers. Focus the process on evidence of production ownership and debugging under pressure.

1
Scope the Role Around API Ownership
Define which APIs the hire will own (e.g., ordering or billing), the on-call expectations, and the integration surface: Azure SQL, Redis, Azure Service Bus, and third-party REST APIs called through typed HttpClients. This filters out candidates who have only implemented isolated tickets inside someone else's architecture.
2
Source Engineers With Production ASP.NET Core Footprints
Look for engineers who answer [asp.net-core] and [entity-framework-core] questions on Stack Overflow, file well-reasoned issues on dotnet/aspnetcore, present at .NET user groups, or contribute to ecosystem libraries such as Serilog, FluentValidation, Polly, or NSwag. Combine 'ASP.NET Core' with 'Entra ID', 'Service Bus', or 'Testcontainers' in LinkedIn boolean strings. Share the job from your Career Page in these channels, and add people who have not applied from Candidate Lookup or by their LinkedIn profile URL.
3
Administer a 45-Minute SkillSauce Performance & Security Assessment
Provide an orders API with production-style defects: a list endpoint issuing one SQL query per order line, a singleton PricingCache that captures the scoped OrdersDbContext, unhandled exceptions leaking stack traces as 500s, and write endpoints that accept any authenticated user. Candidates fix the N+1, resolve the captive dependency, add IExceptionHandler with AddProblemDetails, enforce an authorization policy on the orders.write scope, and add a WebApplicationFactory + Testcontainers SQL Server integration test. Pick the questions from the Question Library, or let TESSA AI generate them when your exact skill mix is missing, and keep AI proctoring on for remote candidates.
4
Use a 20-Minute TESSA AI Interview for Ownership & Trade-Offs
TESSA probes how the candidate handled a real production incident (thread-pool starvation from sync-over-async, SNAT port exhaustion on App Service from creating a new HttpClient per request, a failed EF Core migration during a slot swap), how they negotiate breaking API changes with consumer teams, and how they balance delivery pressure against technical debt. TESSA runs this AI interview in any of 100+ languages and returns a scored report you can share with the team.
5
Run a 60-Minute Live Code Review & Design Session
Ask the candidate to review a pull request containing AddSingleton<IOrderService, OrderService>() where OrderService takes a DbContext, new HttpClient() inside a loop, [Authorize(Roles = 'Admin')] hard-coded across controllers, IOptions<T> expected to pick up runtime config changes, and an async void method. Then have them design an idempotent payment-webhook endpoint backed by an Idempotency-Key header, a unique index in SQL Server, and a Service Bus publish.
6
Close With a Competitive, Ownership-Focused Offer
Benchmark against regional .NET market data — experienced ASP.NET Core engineers are heavily contested by banks, insurers, Microsoft partners, and consultancies — highlight the APIs they will own, and aim to close within 18–25 days.

Pro Tips

Ask what happens when a singleton depends on a scoped DbContext and why the problem may only surface in Development. Strong candidates explain the captive dependency, that scope validation (ValidateScopes) is on by default only in the Development environment, and that in Production the DbContext silently lives for the app's lifetime and is shared across concurrent requests, producing 'A second operation was started on this context instance' errors and stale tracked entities. The fix: make the consumer scoped or create a scope with IServiceScopeFactory.
Probe the options pattern: IOptions<T> is a singleton bound once, IOptionsSnapshot<T> is scoped and recomputed per request, and IOptionsMonitor<T> is a singleton with OnChange notifications. Look for ValidateDataAnnotations().ValidateOnStart() so a missing connection string fails the deployment instead of the first request.
Check EF Core judgment: AsNoTracking and Select projections for read endpoints, AsSplitQuery when multiple collection Includes cause a cartesian explosion, LogTo or Application Insights dependency telemetry to detect N+1, ExecuteUpdateAsync for set-based updates, and applying migrations through idempotent scripts or migration bundles in the pipeline — not Database.Migrate() racing on startup across three App Service instances.
Ask when they would use middleware versus an MVC action filter versus a minimal API endpoint filter. Strong answers note that action filters see bound arguments and ModelState but only for MVC, middleware sees every request, and exception filters miss exceptions thrown in middleware or during result execution — which is why .NET 8's IExceptionHandler plus UseExceptionHandler is the better global error boundary.
Probe rate limiting: the middleware's default RejectionStatusCode is 503, so it should be set to 429; limits are held in each instance's memory, so four App Service instances quadruple the effective limit; and partitioning by client IP behind Azure Front Door is meaningless unless the forwarded headers middleware is configured.

Mid-Level Backend Developer (ASP.NET) Job Description Template

Use this template to attract experienced ASP.NET Core engineers who want end-to-end ownership of production APIs rather than a queue of isolated tickets.

Mid-Level Backend Developer (ASP.NET) Job Description

Role Overview

We're looking for a Mid-Level Backend Developer (ASP.NET) to own core APIs on our ASP.NET Core platform running in Azure. You'll design and ship features end to end — REST endpoints, EF Core persistence on Azure SQL, caching, authorization with Microsoft Entra ID, and asynchronous processing with Azure Service Bus — and you'll be accountable for how those APIs behave in production: latency, error rates, and data integrity.

First 90 Days Deliverables

Days 1–30: Run the [Service Name] API locally with .NET Aspire or Docker Compose (SQL Server, Redis), join the on-call shadow rotation, and ship a performance fix for one of the top-3 slowest endpoints in Application Insights (target: p95 latency down 30% by replacing Include chains with Select projections, adding AsNoTracking and AsSplitQuery where appropriate, and adding a missing index through a reviewed EF Core migration).
Days 31–60: Deliver a new feature slice end to end: versioned endpoints with an accurate OpenAPI document, authorization policies over Entra ID scopes and app roles, an output-cached read path backed by Redis with tag-based eviction on writes, and a WebApplicationFactory + Testcontainers SQL Server suite running in CI.
Days 61–90: Build a BackgroundService that processes Azure Service Bus messages with a fresh DI scope and DbContext per message, add standard resilience handlers (retry, timeout, circuit breaker) to outbound typed HttpClients, apply a token-bucket rate limiting policy to the public search endpoint, publish custom System.Diagnostics.Metrics counters to an Azure Monitor dashboard, and present the design in an architecture review.

Must-Have Requirements

3–6 years of professional C#/.NET development, including at least 2 years building production ASP.NET Core APIs.
Deep understanding of the middleware pipeline, MVC filters and endpoint filters, model binding and validation, built-in DI lifetimes, and the options pattern.
Strong EF Core skills: tracking vs no-tracking queries, loading strategies, migrations, and optimistic concurrency with rowversion tokens.
Experience securing APIs with JWT bearer authentication, Microsoft Entra ID (or another OIDC provider), and policy-based authorization.
SQL Server or Azure SQL performance work: execution plans, indexing, and Query Store.
Automated testing discipline: xUnit, mocking, WebApplicationFactory, and Testcontainers.
Deployment experience with Azure App Service or containers, plus CI/CD in GitHub Actions or Azure DevOps.

Nice-to-Have Skills

SignalR for real-time notifications, or gRPC for internal services.
Messaging with Azure Service Bus, MassTransit, or Wolverine.
Dapper for hot read paths alongside EF Core.
AKS or Azure Container Apps deployments with health-check-based probes.
A current Microsoft Azure developer certification.

Benefits & Mentorship

Competitive mid-level salary plus equity or annual bonus.
Ownership of a core API and a clear path to Senior / Tech Lead, with a staff engineer as your design mentor.
Annual conference budget (.NET Conf, NDC, Microsoft Build) and certification support.
Flexible hybrid/remote work, comprehensive health coverage, and paid on-call compensation.

Need a version for another role or tone? Draft one with the free Job Description Generator.

Targeted Sourcing Channels for Mid-Level ASP.NET Core Engineers

Experienced ASP.NET Core engineers leave public traces of production work: detailed Stack Overflow answers, issues and pull requests on the framework itself, and contributions to the libraries every .NET API depends on. Source where that evidence lives.

SkillSauce

Candidate Lookup

Search by domain and seniority, then narrow by the companies and locations you want to hire from. The people you pick join the same pipeline as your applicants.

SkillSauce

Career Page and LinkedIn Import

Publish the job on your Career Page and share the link on LinkedIn, X and job boards: every applicant lands in the role’s Job Profile. Import a LinkedIn profile by its URL when you spot someone.

Social network

X (Twitter) (opens in a new tab)

x.com

Post the role with hashtags such as #dotnet and #aspnetcore, and join the X Communities where people in the field share their work.

Technical Forum

Stack Overflow [asp.net-core] Tag Contributors (opens in a new tab)

stackoverflow.com

Identify engineers with high-quality answers on middleware ordering, DI lifetimes, authentication schemes, and EF Core query translation. Answer history is a public, timestamped record of production debugging depth.

Open Source Directory

GitHub dotnet/aspnetcore Issue Reporters & Contributors (opens in a new tab)

github.com

Engineers who file reproducible bug reports or API proposals on the ASP.NET Core repository are usually running it in production at scale. Look for thoughtful issues about Kestrel, authentication, rate limiting, or output caching and reach out referencing the specific thread.

Open Source Directory

.NET Foundation Project Contributors (opens in a new tab)

dotnetfoundation.org

The .NET Foundation hosts widely used projects in the ASP.NET Core ecosystem. Contributors to libraries such as Polly, FluentValidation, or NSwag understand the framework's extension points and the real problems teams hit in production.

Package Registry

NuGet Gallery Package Authors (opens in a new tab)

nuget.org

Search NuGet for ASP.NET Core middleware, health check, and authentication extension packages, then review the authors' GitHub profiles. Engineers who publish and maintain packages with real download counts understand versioning, DI extension methods, and API design.

Recruitment Platform

LinkedIn Boolean Search – Production ASP.NET Core Engineers (opens in a new tab)

linkedin.com

Use: ('ASP.NET Core' OR '.NET 8' OR '.NET Core') AND ('Entity Framework Core' OR 'EF Core') AND ('Azure' OR 'App Service' OR 'Service Bus') AND ('Entra ID' OR 'Azure AD' OR 'JWT') NOT ('Intern' OR 'Trainee'). Filter for 3–6 years and titles like Software Engineer II, .NET Developer, or Backend Engineer.

Job boards

Job Boards

Post the job on Indeed and Glassdoor, and on Naukri and foundit for hiring in India. Where a board allows it, use your Career Page link as the apply link, so applicants land in the same Job Profile.

Referrals

Employee Referrals

Ask your team who they have worked with. Referred candidates take the same assessment and interview as everyone else.

Mid-level .NET engineers respond to outreach that speaks their language — real production problems in ASP.NET Core and Azure, real ownership, and a respectful, practical process.

LinkedIn Post

Hiring: Mid-Level Backend Developer (ASP.NET) You've run ASP.NET Core APIs in production. You've hunted a captive DbContext inside a singleton, untangled an EF Core cartesian explosion with AsSplitQuery, and been paged for thread-pool starvation at 2 a.m. Come own a core API with us. Stack: ASP.NET Core on .NET 8+, EF Core, Azure SQL, Entra ID, Redis output caching, Azure Service Bus, App Service, Application Insights You'll own: [API Domain] — endpoints, data model, performance, and on-call Growth: clear path to Senior / Tech Lead, conference budget Skip the trivia rounds — start with a 45-minute practical SkillSauce challenge: [SkillSauce Assessment Link] #dotnet #aspnetcore #efcore #Azure #BackendEngineering #Hiring

Show template

Twitter / X Post

Show template

Know why a scoped DbContext inside a singleton works fine in dev and melts down in prod? We're hiring a Mid-Level ASP.NET Core Engineer (EF Core, Entra ID, Redis, Service Bus) to own a core API end to end. 45-min practical test, no whiteboards: [SkillSauce Assessment Link] #dotnet #aspnetcore #BackendJobs

LinkedIn Direct Message

Hi [Candidate Name], I noticed your experience at [Current Company] running ASP.NET Core APIs on [Azure App Service / AKS] — and your [Stack Overflow answer / blog post / GitHub issue] on [topic, e.g., JWT claim mapping in .NET 8] was genuinely useful. At [Company Name] we're looking for a Mid-Level Backend Engineer to own our [API Domain] API: EF Core performance work on Azure SQL, Entra ID authorization policies, output caching, and Service Bus integrations — with real production ownership and a fair on-call rotation. Our process is short and practical: a 45-minute SkillSauce exercise based on a real slow endpoint we fixed last year: [SkillSauce Assessment Link]. Open to a 20-minute chat to hear more? Best, [Your Name]

Show template

Email Sequence for Mid-Level ASP.NET Core Candidates

Lead with the concrete API and production problems the candidate will own, explain the two-part evaluation clearly, and make the offer about scope as much as salary.

Cold Sourcing

Subject: Own our [API Domain] API — ASP.NET Core Engineer at [Company Name]

Show template

Hi [Candidate Name], Your work on [Project/Company] caught my eye — particularly [specific detail, e.g., moving a .NET Framework Web API to ASP.NET Core with minimal downtime]. At [Company Name], our [API Domain] API handles [X] requests per day on ASP.NET Core, Azure SQL, and Azure Service Bus. We're hiring a Mid-Level Backend Developer (ASP.NET) to own it: tune EF Core queries, harden Entra ID authorization, add output caching and rate limiting, and build integrations that don't lose messages. Our process respects your time: a 45-minute SkillSauce practical based on a real performance issue from our codebase, a 20-minute TESSA AI conversation, and a single live review-and-design session. Preview the challenge here: [SkillSauce Assessment Link] Would you be open to a 15-minute call this week? Best regards, [Your Name] [Your Title], [Company Name]

Interview Invite

Subject: Technical evaluation: Mid-Level Backend Developer (ASP.NET) at [Company Name]

Show template

Hi [Candidate Name], Thanks for a great conversation! We'd love to move you to our technical evaluation, which has two parts you can complete within the next 3 business days: 1. SkillSauce Practical Assessment (45 mins): You'll work in an ASP.NET Core orders API with production-style defects. Eliminate an EF Core N+1 query, fix a captive DbContext dependency, add ProblemDetails error handling with IExceptionHandler, enforce a JWT scope-based authorization policy, and add a Testcontainers-backed integration test: [SkillSauce Assessment Link] 2. TESSA AI Interview (20 mins): A conversational interview on production incidents you've handled, API versioning decisions, and how you balance delivery with technical debt: [TESSA Interview Link] After we review your results, we'll schedule a 60-minute live session with [Interviewer Name], our Staff Engineer, covering a pull-request review and a small design exercise. Best regards, [Your Name] [Company Name]

Offer Letter

Subject: Formal Offer: Backend Developer (ASP.NET) at [Company Name]

Show template

Dear [Candidate Name], On behalf of [Company Name], I'm excited to offer you the position of Backend Developer (ASP.NET)! The team was impressed by how quickly you spotted the captive DbContext in your SkillSauce assessment and by your idempotent webhook design in the live session. Offer Summary: • Position: Mid-Level Backend Developer (ASP.NET) • Base Salary: [Salary Amount] per annum • Equity / Bonus: [Equity Grant or Bonus Structure] • Start Date: [Start Date] • Reporting To: [Engineering Manager Name] • Design Mentor: [Staff Engineer Name], Staff Engineer • API Ownership: [API Domain] API, with a 90-day onboarding plan • On-Call: [Rotation Frequency] rotation with [On-Call Compensation] • Learning: [Amount] annual budget for conferences (.NET Conf, NDC, Microsoft Build) and Azure certifications • Equipment: Laptop or workstation of choice, Visual Studio Enterprise or JetBrains Rider, home-office stipend • Benefits: Comprehensive health coverage, [PTO Days] days PTO, retirement matching Please review the attached agreement and return it by [Offer Expiration Date]. We're looking forward to building with you! Warm regards, [Your Name] [Company Name]

Mid-Level ASP.NET Core SkillSauce & TESSA Assessment Blueprint

An evaluation that reproduces the failure modes mid-level ASP.NET Core engineers must handle in production — EF Core misuse, DI lifetime bugs, leaky error handling, and inconsistent authorization — and grades them objectively.

45 mins

SkillSauce Mid-Level ASP.NET Core Performance, DI & Security Assessment

Candidates inherit an ASP.NET Core orders API where GET /api/customers/{id}/orders issues 101 SQL statements for 100 orders, a singleton PricingCache captures the scoped OrdersDbContext, unhandled exceptions return raw stack traces, and POST /api/orders is open to any authenticated caller. They must reduce the endpoint to a bounded number of queries without breaking pagination, fix the lifetime bug, return RFC 7807 ProblemDetails via IExceptionHandler, require the orders.write scope through a named authorization policy, add output caching with tag eviction on writes, and add an integration test using WebApplicationFactory with ConfigureTestServices and a Testcontainers SQL Server. Automated grading counts SQL commands via an EF Core interceptor and runs a hidden authorization test suite.

Focus:: EF Core N+1 and cartesian-explosion diagnosis, DI lifetimes and captive dependencies, IExceptionHandler with ProblemDetails, JWT bearer policy-based authorization, output caching, and WebApplicationFactory + Testcontainers integration testing.

20 mins

TESSA AI Production Ownership & Trade-Off Interview

TESSA asks the candidate to walk through a real incident they owned (e.g., thread-pool starvation, HttpClient socket or SNAT exhaustion, or an EF Core migration that locked a hot table), how they versioned a breaking API change for downstream consumers, and how they decide between shipping and refactoring. Scoring emphasizes structured root-cause reasoning, ownership language, and clear communication of trade-offs. TESSA AI runs it as an AI interview and returns a scored report for the hiring team.

Focus:: Incident response, API contract evolution, technical debt prioritization, and cross-team collaboration.

Why This Assessment Mix

Mid-level ASP.NET Core engineers are hired to own APIs, and the most expensive production failures in .NET web codebases come from EF Core misuse, DI lifetime mistakes that only appear under concurrency, error handling that leaks internals, and authorization rules scattered across controllers. The SkillSauce task reproduces these failure modes in a real ASP.NET Core host and grades them objectively (SQL command counts, authorization tests, integration tests), while TESSA verifies the ownership mindset and communication needed to run an API in production. The combination reliably separates engineers who have operated ASP.NET Core under load from those who have only built greenfield tutorial APIs.

You can run tests like these in SkillSauce: build an IT skills assessment from the test library and turn on AI proctoring for remote candidates.

Ownership & Collaboration Rubric for Mid-Level ASP.NET Core Engineers

These questions assess production ownership, API stewardship, risk communication, and the code review habits that make a mid-level ASP.NET Core engineer a force multiplier.

Tell me about the most serious production incident you handled in an ASP.NET Core API. How did you find the root cause, and what did you change afterwards?

Why it matters: Mid-level engineers are expected to own APIs operationally, not just write code.
What to listen for: Green flags: concrete signals (Application Insights failure rates and dependency durations, dotnet-counters thread-pool queue length, SQL Server wait stats, App Service SNAT port metrics), a mitigation such as scaling out or toggling a feature flag followed by a durable fix (async all the way, IHttpClientFactory, an index), and a blameless post-mortem with action items. Red flags: blaming others, no data, or a 'fix' that only restarted the App Service.

You need to rename a field in a public REST API used by three other teams. How do you roll it out?

Why it matters: Tests API contract discipline and cross-team communication.
What to listen for: Green flags: an additive change first (serialize both properties), marking the old field deprecated in the OpenAPI document, introducing a new API version with Asp.Versioning and sunset headers if the change is breaking, contract or consumer tests, and telemetry on old-field usage before removal. Red flags: renaming the C# property and letting System.Text.Json break consumers silently.

Describe a time you pushed back on a feature deadline because of a technical risk. What happened?

Why it matters: Reveals judgment and the ability to communicate risk to product stakeholders.
What to listen for: Green flags: quantified risk (data loss from a non-idempotent endpoint, an authorization gap, an unindexed query on a large table), proposed alternatives such as a Microsoft.FeatureManagement flag or a phased rollout through deployment slots, and alignment reached with product. Red flags: silently cutting corners, or refusing without offering options.

How do you review a pull request from a junior engineer that works but has design problems?

Why it matters: Mid-level engineers multiply the team through reviews.
What to listen for: Green flags: separating blocking issues (a DbContext captured by a singleton, entities returned from controllers, authorization checks hand-rolled inside actions) from preferences, explaining the why with links to team conventions or Microsoft docs, and offering to pair. Red flags: rewriting the code themselves or nitpicking formatting that an .editorconfig and analyzers should enforce.

TESSA, the SkillSauce AI interviewer, can run a structured first-round interview built around questions like these. See how TESSA AI interviews work.

Verified Mid-Level ASP.NET Core Technical Questions

Five MEDIUM-tier multiple-choice questions taken verbatim from the SkillSauce ASP.NET Core question bank (it/question_bank/ASP.NET Core.json), covering middleware placement, DbContext lifetime, EF Core SQL diagnostics, claims-based authorization policies, and environment-specific configuration.

In an ASP.NET Core application, you need to implement custom middleware that logs the duration of each HTTP request for performance analysis. Where should this middleware ideally be placed in the request pipeline?

Medium

aAfter UseStaticFiles to log only dynamic content requests
bAfter UseEndpoints to finalize endpoint processing first
cAfter UseRouting to capture route-specific timings
dAt the very beginning of the pipeline to capture the entire request durationCorrect

Explanation: Placing the middleware at the beginning ensures that the entire processing time—from the moment a request enters until the response is sent—is captured, providing a true measure of performance.

Why it matters: Tests the mental model of middleware as nested delegates: code before await next(context) runs on the way in and code after it runs on the way out, so the first registered middleware wraps everything else. Follow up: middleware placed after the terminal endpoint middleware only runs for unmatched requests; with WebApplication, routing is applied before your middleware unless you call UseRouting explicitly, so even an early middleware can read HttpContext.GetEndpoint(); and ASP.NET Core 8 already emits the http.server.request.duration metric, so custom timing is often unnecessary.

When registering a DbContext for an ASP.NET Core application, which service lifetime is most appropriate to avoid threading issues while ensuring efficient database operations?

Medium

aSingleton, to share a single instance across the application
bScoped, to create one instance per HTTP requestCorrect
cTransient, to create a new instance on every injection
dPerCall, to generate an instance per method call

Explanation: DbContext is not thread-safe and should be scoped per HTTP request to ensure that it is used safely and efficiently within the context of a single request.

Why it matters: AddDbContext registers the context as scoped by default because DbContext is not thread-safe and its change tracker grows with every query. Follow up on the failure modes: injecting it into a singleton or BackgroundService (captive dependency), running Task.WhenAll over queries on the same context ('A second operation was started on this context instance'), and when to use AddDbContextPool or IDbContextFactory<T> instead. 'PerCall' is not a lifetime in Microsoft.Extensions.DependencyInjection.

In a production ASP.NET Core application using EF Core, performance issues emerge due to suboptimal SQL queries. Which practical technique would allow you to diagnose the problem without making initial code changes?

Medium

aIncrease the lifetime of the DbContext
bEnable logging of SQL queries via LoggerFactoryCorrect
cEnable SQL Server query plan caching
dSwitch to using lazy loading proxies

Explanation: Enabling logging for SQL queries allows developers to inspect the generated SQL and identify performance bottlenecks without altering the existing codebase immediately.

Why it matters: Checks EF Core diagnostics fluency: raising the Microsoft.EntityFrameworkCore.Database.Command log category to Information through configuration logs every generated SQL statement with its duration, without a redeploy of code. Strong candidates add ToQueryString() for one-off inspection, Application Insights dependency telemetry, and SQL Server Query Store, and know that EnableSensitiveDataLogging belongs only in development. Option d is a trap — lazy loading proxies are a common cause of N+1 queries, not a cure.

An ASP.NET Core API must secure endpoints using policies that rely on custom claims provided by an external identity provider. Which approach best meets this requirement?

Medium

aHard-code claim checks directly in the controller actions
bUse role-based authorization exclusively
cApply anonymous access and handle security in the client application
dCreate a custom AuthorizationPolicy to evaluate the necessary claimsCorrect

Explanation: A custom AuthorizationPolicy allows fine-grained control over access based on custom claims, accommodating dynamic and external identity provider-driven values without embedding logic in controllers.

Why it matters: Evaluates policy-based authorization: AddAuthorizationBuilder().AddPolicy('CanApproveRefunds', p => p.RequireClaim('department', 'finance')) applied with [Authorize(Policy = ...)] or RequireAuthorization on minimal APIs. Go deeper: a custom IAuthorizationRequirement with an AuthorizationHandler for logic beyond claim presence, resource-based checks through IAuthorizationService, Entra ID's scp and roles claims, setting MapInboundClaims = false so JWT claim names are not rewritten, and the cost of an IClaimsTransformation that hits the database on every request.

You need to configure an ASP.NET Core application to load environment-specific settings in a way that adheres to modern, best practices. Which method best satisfies this real-world requirement?

Medium

aUtilize environment variables to override settings in appsettings.json as per the active environmentCorrect
bHard-code environment-specific logic within the Startup class
cUse a single appsettings.json file without any overrides
dMaintain separate configuration files and manually switch them based on deployment

Explanation: Environment variables provide a robust and standard mechanism for overriding configuration values in appsettings.json, enabling dynamic adjustments based on deployment contexts without code changes.

Why it matters: Tests understanding of configuration provider layering in WebApplication.CreateBuilder: appsettings.json, then appsettings.{Environment}.json, then user secrets in Development, then environment variables, then command-line arguments, with later sources winning. Follow up on the double-underscore convention for nested keys (ConnectionStrings__Default), how App Service application settings surface as environment variables, ASPNETCORE_ENVIRONMENT, and binding sections to IOptions<T> with ValidateOnStart.

Need more questions for this stack? Browse sample questions by skill in the SkillSauce Question Library.

Constructive Rejection Templates for Mid-Level ASP.NET Core Candidates

Experienced .NET engineers talk to each other at user groups and conferences. Specific, respectful feedback protects your reputation in the local .NET community and keeps strong near-miss candidates warm.

Post-Assessment Rejection

Subject: Update on your Backend Developer (ASP.NET) application at [Company Name]

Show template

Hi [Candidate Name], Thank you for completing the SkillSauce assessment for our Mid-Level Backend Developer (ASP.NET) role — we appreciate the time and focus it takes. After reviewing your SkillSauce report, we won't be moving forward at this time. The areas where your submission fell short of what this role needs on day one were [e.g., eliminating the EF Core N+1 query without breaking pagination / resolving the singleton-to-scoped DbContext dependency / enforcing the scope-based authorization policy]. Because this role involves immediate ownership of a production API, we have to weigh these heavily. This feedback reflects a single timed exercise, not your overall ability. We'd be happy to consider you for future openings and wish you the best in your search. Kind regards, [Your Name] [Company Name]

Post-Interview Rejection

Subject: Thank you for interviewing with [Company Name]

Show template

Hi [Candidate Name], Thank you for the time you invested in our interview process, including the live review-and-design session with [Interviewer Name]. The team especially valued [specific strength, e.g., your clear explanation of why IOptionsMonitor was the right fit for the feature-toggle service]. After a lot of deliberation, we've decided to move forward with another candidate whose production experience aligns more closely with [specific need, e.g., our Azure Service Bus-heavy integration roadmap]. If it's useful, our interviewers felt that deeper hands-on experience with [e.g., Entra ID authorization policies / EF Core concurrency handling] would strengthen your profile for similar roles. We'd like to stay in touch — I'll reach out if a role opens that's a stronger match. Thank you again, and best of luck. Warm regards, [Your Name] [Company Name]

Senior level

Senior Backend Developer (ASP.NET)

Experience: 6+ Years
Average time to hire: 25 - 40 Days

Core tech stack

ASP.NET Core internals (Kestrel, hosting, endpoint routing)
.NET 8 → .NET 10 LTS upgrades & Native AOT
EF Core at scale (compiled queries, DbContext pooling, ExecuteUpdate)
Microsoft Entra ID, OAuth 2.0 / OIDC & Data Protection
Output caching, HybridCache & Azure Managed Redis
SignalR scale-out (Azure SignalR Service)
Azure Service Bus + transactional outbox
YARP, Azure API Management & Azure Front Door
OpenTelemetry & Azure Monitor
AKS, Azure Container Apps & App Service

How to Hire a Senior Backend Developer (ASP.NET)

Senior ASP.NET Core engineers (6+ years) set the technical direction for a fleet of .NET APIs. Beyond deep framework knowledge — Kestrel and the hosting model, endpoint routing, the authentication handler pipeline, DI container internals, and EF Core's query pipeline — they make decisions that hold up under scale and failure: consistency across services (transactional outbox, idempotent consumers on Azure Service Bus), multi-instance correctness (Data Protection key rings, distributed output cache and rate limiting, SignalR backplanes), resilience with Microsoft.Extensions.Http.Resilience, gateway topology with YARP, API Management, and Front Door, observability with OpenTelemetry and Azure Monitor, and runtime choices such as Native AOT or the .NET 8 to .NET 10 LTS upgrade. Evaluate for architectural judgment, operational depth on Azure, and the ability to raise the engineering bar across teams.

1
Align on Architectural Mandate and Scope
Decide whether you are hiring a senior IC to lead a domain, a tech lead for a squad, or a platform engineer owning shared internal NuGet packages (service defaults, authentication, telemetry). Document the decisions they will drive: moving the fleet from .NET 8 to .NET 10 LTS before .NET 8 leaves support, migrating remaining .NET Framework ASP.NET MVC/Web API apps incrementally behind YARP, consolidating authentication on Microsoft Entra ID, or adopting Native AOT for latency-sensitive services.
2
Source Proven ASP.NET Core Architects
Target Microsoft MVPs in Developer Technologies and Azure, NDC and .NET Conf speakers, long-form .NET bloggers, and contributors to dotnet/aspnetcore, YARP, OpenTelemetry .NET, Polly, or messaging libraries such as MassTransit and Wolverine. Referrals from former colleagues carry unusual weight at this level. Senior people rarely apply, so search Candidate Lookup by domain, seniority, company and location and reach out first with their available contact details.
3
Administer a 60-Minute SkillSauce Distributed Systems Assessment
Present a multi-service ASP.NET Core system (orders API, payment worker, notifications SignalR hub) running two instances each. A Service Bus publish after SaveChangesAsync loses messages on crashes, duplicate deliveries double-charge customers, the payment HttpClient has no timeouts or circuit breaker, SignalR notifications only reach clients connected to one instance, and antiforgery tokens fail after scale-out because Data Protection keys are not shared. Candidates implement an EF Core outbox, idempotent consumers, a standard resilience handler, a SignalR backplane, and a persisted key ring. Set it up in IT Assessments with a coding test in any of 60+ languages, and keep AI proctoring on so a longer remote session stays fair.
4
Deploy a 25-Minute TESSA AI Architecture & Leadership Interview
TESSA explores how the candidate led a major migration (e.g., .NET Framework to ASP.NET Core, or App Service to AKS), how they resolve architectural disagreements between teams, and how they mentor mid-level engineers. Responses are scored for strategic thinking and influence without authority. TESSA runs this AI interview in any of 100+ languages, and a Behavioural round can follow to probe how they lead.
5
Conduct a 90-Minute System Design Deep Dive
Have the candidate design a high-throughput order platform on ASP.NET Core in Azure: Front Door and API Management or YARP at the edge, App Service vs Azure Container Apps vs AKS, Azure SQL connection pool sizing (pods × Max Pool Size against the database tier's session and worker limits), caching tiers (output caching plus HybridCache over Redis), consistency via outbox and sagas, and SLOs tracked with OpenTelemetry. Push on failure scenarios: an Azure SQL failover, Service Bus throttling, and a burst that triggers thread-pool starvation.
6
Hold a Leadership & Cross-Functional Panel
Include an engineering manager and a product or security partner to evaluate how the candidate writes ADRs, explains trade-offs to non-engineers, and sets standards such as a shared ServiceDefaults package, secure-by-default authentication, and API design guidelines.
7
Close With a Senior-Calibrated Offer
Senior ASP.NET Core architects are heavily recruited by fintech, insurers, Microsoft partners, and Microsoft itself. Present scope, autonomy, and compensation (including equity) clearly, and target a decision within 25–40 days.

Pro Tips

Ask how they would diagnose p99 latency spikes while CPU stays low. Strong answers reach for dotnet-counters (thread-pool queue length and thread count climbing), dotnet-stack or dotnet-dump to find threads blocked in .Result, .Wait(), or synchronous I/O, and fix the sync-over-async root cause rather than raising ThreadPool.SetMinThreads as a permanent band-aid.
Probe Native AOT trade-offs: WebApplication.CreateSlimBuilder, the Request Delegate Generator for minimal APIs, and System.Text.Json source generation versus what is not supported (MVC controllers, Razor views, reflection-heavy libraries) and EF Core's limited, experimental AOT story. Good seniors tie the decision to evidence — scale-to-zero cold starts on Azure Container Apps, container density — not novelty.
Test multi-instance correctness: Data Protection keys persisted to Blob Storage and protected with Key Vault, in-memory output cache and rate limiter state multiplying across instances unless backed by Redis or enforced at API Management, SignalR needing Azure SignalR Service or a Redis backplane, and the forwarded headers middleware with known proxies behind Front Door or Application Gateway so scheme, host, and client IP are correct.
Check EF Core at scale: AddDbContextPool and its state-reset caveats, EF.CompileAsyncQuery for hot paths, ExecuteUpdateAsync and ExecuteDeleteAsync for set-based writes, and the fact that EnableRetryOnFailure on Azure SQL rejects user-initiated transactions unless they are wrapped in Database.CreateExecutionStrategy().ExecuteAsync.
Ask how they would roll out structured logging, OpenTelemetry tracing, health checks, and resilience defaults to 30 APIs. Strong candidates propose an internal NuGet package exposing an AddServiceDefaults()-style extension (the .NET Aspire pattern) with versioned releases, rather than copy-pasted Program.cs blocks.

Senior Backend Developer (ASP.NET) Job Description Template

Use this template to attract senior ASP.NET Core engineers and architects who want to set direction for a .NET platform on Azure, not just deliver tickets within one.

Senior Backend Developer (ASP.NET) Job Description

Role Overview

We are hiring a Senior Backend Developer (ASP.NET) to lead the architecture of our .NET platform — [N] ASP.NET Core APIs and workers running on Azure ([App Service / Azure Container Apps / AKS]) and processing [X] transactions per day. You will set technical direction, own the hardest reliability and performance problems, and raise the bar for every engineer through design reviews, mentorship, and shared platform packages.

First 90 Days Deliverables

Days 1–30: Audit the service landscape — .NET and ASP.NET Core versions (anything still on .NET 6/7 or approaching .NET 8 end of support), middleware pipelines and authentication configuration, Azure SQL utilization, Service Bus topology, and Application Insights SLO dashboards. Publish an Architecture Decision Record summarizing the top five risks and a sequenced remediation plan.
Days 31–60: Lead the design and first implementation of a transactional outbox (EF Core + Azure Service Bus) for the order flow, with idempotent consumers, a dead-letter handling strategy, and standard resilience handlers around the payment provider. Pair with mid-level engineers to land it in two services.
Days 61–90: Ship an internal ServiceDefaults NuGet package that standardizes OpenTelemetry with the Azure Monitor exporter, liveness and readiness health check endpoints, ProblemDetails, forwarded headers, and Data Protection key storage; run a pilot of the .NET 10 upgrade (or Native AOT on one minimal API service) with before/after results from Azure Load Testing.

Must-Have Requirements

6+ years of backend engineering with deep, production-scale expertise in ASP.NET Core internals: Kestrel, middleware and endpoint routing, the authentication/authorization pipeline, DI container behavior, and the options/configuration system.
Proven experience designing distributed systems on .NET: service boundaries, outbox and saga patterns, idempotency, and eventual consistency with Azure Service Bus or similar brokers.
Advanced EF Core and SQL Server / Azure SQL tuning: execution plans, Query Store, locking and isolation levels, connection pool sizing, and compiled queries.
Securing APIs at scale with Microsoft Entra ID, OAuth 2.0 / OIDC flows, managed identities, and Key Vault.
Operating ASP.NET Core in Azure: App Service deployment slots, Azure Container Apps or AKS probes and autoscaling, graceful shutdown, and container memory/GC settings.
Strong observability practice with OpenTelemetry, Azure Monitor / Application Insights, and SLO-based alerting.
A track record of mentoring engineers and leading cross-team initiatives through ADRs and design reviews.

Nice-to-Have Skills

YARP-based gateways or BFFs, and Azure API Management policy design.
SignalR at scale with Azure SignalR Service, or gRPC for internal service-to-service traffic.
Native AOT, Request Delegate Generator, and System.Text.Json source generation in production.
Large migrations: .NET Framework ASP.NET to ASP.NET Core (incremental, strangler-fig), on-prem IIS to Azure.
Azure architecture certification (e.g., AZ-305) and .NET Aspire for local orchestration.

Benefits & Mentorship

Senior/Staff-level compensation with meaningful equity.
Direct influence over platform architecture and engineering standards, plus a peer-mentoring circle with our Principal Engineers.
Generous conference and speaking budget (NDC, .NET Conf, Microsoft Build).
Flexible remote work, comprehensive health benefits, and sabbatical eligibility.

Need a version for another role or tone? Draft one with the free Job Description Generator.

Sourcing Channels for Senior ASP.NET Core Engineers & Architects

Senior ASP.NET Core talent is rarely on job boards. Find them through the Microsoft MVP program, conference speaker rosters, and commit history on the projects that define modern .NET web architecture, then reach out with talk- or contribution-specific context.

SkillSauce

Candidate Lookup

Senior people rarely apply. Search by domain and seniority, narrow by company and location, and reach out first with their available contact details.

SkillSauce

Career Page and LinkedIn Import

Publish the job on your Career Page and share the link on LinkedIn, X and job boards: every applicant lands in the role’s Job Profile. Import a LinkedIn profile by its URL when you spot someone.

Social network

X (Twitter) (opens in a new tab)

x.com

Post the role with hashtags such as #dotnet and #aspnetcore, and join the X Communities where people in the field share their work.

Expert Directory

Microsoft MVP Directory (opens in a new tab)

mvp.microsoft.com

Search for MVPs in the Developer Technologies and Azure categories. Many are hands-on architects who blog and speak about ASP.NET Core performance, authentication, and Azure hosting. Reference a specific post or talk in your outreach; generic messages are ignored.

Industry Conference

NDC Conferences Speakers (opens in a new tab)

ndcconferences.com

NDC (Oslo, London, Sydney, and more) is one of the largest independent developer conference series with a strong .NET track. Speakers on ASP.NET Core, distributed systems, and Azure architecture are prime senior and staff candidates.

Industry Conference

.NET Conf Speakers & Community Sessions (opens in a new tab)

dotnetconf.net

Microsoft's annual virtual .NET conference features community speakers alongside the product team. Community presenters on ASP.NET Core, .NET Aspire, and Azure deployments have proven depth and communication skills.

Open Source Directory

GitHub YARP (microsoft/reverse-proxy) Contributors (opens in a new tab)

github.com

Contributors and well-reasoned issue authors on YARP work on gateways, BFFs, and incremental .NET Framework migrations at scale — exactly the infrastructure-level ASP.NET Core experience senior roles need.

Recruitment Platform

LinkedIn Recruiter – Senior ASP.NET Core Architect Search (opens in a new tab)

linkedin.com

Use: ('ASP.NET Core' OR '.NET') AND ('Architect' OR 'Staff' OR 'Principal' OR 'Tech Lead') AND ('Azure Service Bus' OR 'Event-Driven' OR 'Microservices') AND ('AKS' OR 'Container Apps' OR 'App Service') AND ('Entra ID' OR 'Azure AD'). Prioritize profiles listing migrations, ADRs, MVP status, or conference talks.

Developer community

Stack Overflow (opens in a new tab)

stackoverflow.com

Find people who answer questions in the tags your stack uses: their answers show how they reason and explain.

Job boards

Job Boards

Post the job on Indeed and Glassdoor, and on Naukri and foundit for hiring in India. Where a board allows it, use your Career Page link as the apply link, so applicants land in the same Job Profile.

Referrals

Employee Referrals

Ask your leaders who they would hire again, then put referred candidates through the same assessment and interview as everyone else.

Senior .NET engineers ignore generic recruiter messages. Lead with architectural scope, concrete hard problems in ASP.NET Core and Azure, and a reference to their public work.

LinkedIn Post

We're hiring a Senior Backend Developer (ASP.NET) to lead our .NET platform architecture. If you've built an EF Core outbox on Azure Service Bus, chased thread-pool starvation with dotnet-counters, and moved a fleet of APIs across .NET LTS versions without downtime — this role is built for you. Scope: technical direction for [N] ASP.NET Core services on Azure Stack: .NET 8 → 10, ASP.NET Core, EF Core, Azure SQL, Service Bus, Entra ID, YARP, OpenTelemetry, AKS / Container Apps Impact: shape platform standards, mentor engineers, own the hardest reliability problems Our senior process is respectful and practical — start with a 60-minute distributed-systems SkillSauce challenge: [SkillSauce Assessment Link] #dotnet #aspnetcore #SoftwareArchitecture #Azure #Microservices #StaffEngineer

Show template

Twitter / X Post

Show template

Shared your Data Protection key ring across instances? Scaled SignalR past one node? Know why EnableRetryOnFailure hates your BeginTransaction? We're hiring a Senior ASP.NET Core Engineer to lead our .NET platform on Azure. 60-min practical, no trivia: [SkillSauce Assessment Link] #dotnet #aspnetcore #Azure

LinkedIn Direct Message

Hi [Candidate Name], I really enjoyed your [NDC talk / blog post / YARP contribution] on [topic] — especially your point about [specific detail]. I'm reaching out because [Company Name] is looking for a Senior Backend Engineer to set the technical direction for our ASP.NET Core platform: [N] services on Azure, a Service Bus event backbone in progress, and a .NET 10 upgrade ahead. You'd have real architectural ownership and a team eager to learn from you. If you're open to it, I'd love to set up a confidential 30-minute conversation with our CTO. Our technical evaluation is a 60-minute practical system challenge rather than algorithm drills: [SkillSauce Assessment Link] Best regards, [Your Name]

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Email Sequence for Senior ASP.NET Core Candidates

Senior outreach should read like a peer-to-peer conversation: specific scope, honest challenges in the .NET platform, a compact process, and an offer that spells out autonomy and impact.

Cold Sourcing

Subject: Lead the architecture of our ASP.NET Core platform at [Company Name]

Show template

Hi [Candidate Name], I've been following your work on [Project/Talk/Article], and your perspective on [specific topic, e.g., incrementally migrating .NET Framework apps to ASP.NET Core behind YARP] is exactly what our team needs. [Company Name] runs [N] ASP.NET Core services on Azure handling [X] transactions per day. Over the next year we're building a Service Bus event backbone with a transactional outbox, standardizing OpenTelemetry and health checks through a shared ServiceDefaults package, and upgrading the fleet to .NET 10. We're looking for a Senior Backend Developer (ASP.NET) to lead these decisions and mentor a team of [Team Size] .NET engineers. Our senior process is focused and respectful of your time: a 60-minute SkillSauce distributed-systems exercise, a 25-minute TESSA AI conversation, and a system design deep dive with our CTO. Preview the challenge: [SkillSauce Assessment Link] Would you be open to a confidential conversation in the next couple of weeks? Best regards, [Your Name] [Your Title], [Company Name]

Interview Invite

Subject: Senior ASP.NET Core Engineer — technical evaluation at [Company Name]

Show template

Hi [Candidate Name], Thank you for the conversation with [Hiring Manager Name]. We're excited to invite you to our technical evaluation, which you can complete within the next 5 business days: 1. SkillSauce Distributed Systems Assessment (60 mins): A multi-instance ASP.NET Core system (orders API, payment worker, SignalR notifications hub) with consistency, resilience, and scale-out problems. You'll implement an EF Core transactional outbox with Azure Service Bus, idempotent consumers, resilience handlers for the payment client, a SignalR backplane, and a shared Data Protection key ring: [SkillSauce Assessment Link] 2. TESSA AI Interview (25 mins): A conversational interview on architectural decisions you've led, migrations, cross-team influence, and mentoring: [TESSA Interview Link] Afterwards, we'll schedule a 90-minute system design deep dive with our CTO and Principal Engineer, followed by a leadership panel. We look forward to it! [Your Name] [Company Name]

Offer Letter

Subject: Offer of Employment: Senior Backend Developer (ASP.NET) at [Company Name]

Show template

Dear [Candidate Name], It's my great pleasure to offer you the position of Senior Backend Developer (ASP.NET) at [Company Name]. Your outbox design in the SkillSauce assessment and your handling of Azure SQL failover and thread-pool starvation scenarios during the system design deep dive convinced the whole panel that you're the right person to lead our platform architecture. Offer Summary: • Position: Senior Backend Developer (ASP.NET) • Base Salary: [Salary Amount] per annum • Equity: [Equity Grant] vesting over [Vesting Schedule] • Annual Bonus: [Bonus Target] • Start Date: [Start Date] • Reporting To: [CTO / VP Engineering Name] • Executive Sponsor & Mentor: [Principal Engineer or CTO Name] • Scope: Technical direction for the .NET platform, including the event backbone and shared platform packages • Learning & Speaking: [Amount] annual budget for conferences (NDC, .NET Conf, Microsoft Build), speaking, and Azure certifications • Equipment: Workstation of choice, Visual Studio Enterprise or JetBrains Rider, Azure sandbox subscription, home-office stipend • Benefits: Premium health coverage, [PTO Days] days PTO, retirement matching, sabbatical eligibility after [N] years Please return the signed agreement by [Offer Expiration Date]. We're excited to build the next chapter of our platform with you. Warm regards, [Your Name] [Company Name]

Senior ASP.NET Core SkillSauce & TESSA Assessment Blueprint

A chaos-graded, multi-instance distributed systems exercise paired with a leadership interview, designed to measure how a senior ASP.NET Core engineer designs for failure and drives adoption across teams.

60 mins

SkillSauce Senior ASP.NET Core Distributed Systems & Scale-Out Assessment

Candidates receive a three-service ASP.NET Core solution orchestrated with .NET Aspire (orders API, payment worker, notifications SignalR hub), each running two instances behind a YARP gateway, with SQL Server and a Service Bus emulator. Payment failures leave orders stuck in Pending, duplicate deliveries double-charge customers, the payment HttpClient hangs without timeouts, notifications only reach clients on one instance, antiforgery validation fails intermittently, and the readiness endpoint reports Healthy before the cache is warm. Candidates must add an outbox table written in the same SaveChangesAsync transaction with a background relay, make consumers idempotent on a business key, add AddStandardResilienceHandler with tuned timeouts, configure a SignalR backplane, persist the Data Protection key ring, and split health checks into tagged liveness and readiness endpoints. A chaos harness grades correctness under injected crashes, duplicate messages, and downstream latency.

Focus:: EF Core transactional outbox with Azure Service Bus, idempotent consumers, Microsoft.Extensions.Http.Resilience, SignalR scale-out, Data Protection key sharing, forwarded headers, and readiness vs liveness health checks.

25 mins

TESSA AI Architecture & Technical Leadership Interview

TESSA runs an adaptive interview probing a major architecture decision the candidate led (e.g., a .NET Framework to ASP.NET Core migration, a move from App Service to AKS, or adopting Native AOT), how they handled dissent, how they measured success, and how they grow senior engineers. Responses are evaluated for depth of reasoning, ownership of outcomes, and clarity for both technical and non-technical audiences. TESSA AI runs it as an AI interview and returns a scored report for the hiring team.

Focus:: Architectural decision-making, migration leadership, cross-team influence, mentoring, and communicating trade-offs to executives.

Why This Assessment Mix

Senior ASP.NET Core engineers rarely fail on framework syntax; they fail on judgment — a consistency model that loses messages under partial failure, a design that only works on a single instance, resilience settings that turn a slow dependency into a thread-pool meltdown, or standards that teams never adopt. The 60-minute chaos-graded SkillSauce assessment shows how a candidate actually designs for failure and scale-out in a realistic Azure-shaped ASP.NET Core system, and TESSA's leadership interview evaluates the influence and communication that determine whether those designs get adopted across the fleet. Together they predict architectural impact far more reliably than years of .NET experience or a list of Azure services on a CV.

You can run tests like these in SkillSauce: build an IT skills assessment from the test library and turn on AI proctoring for remote candidates.

Architecture & Leadership Rubric for Senior ASP.NET Core Engineers

These questions evaluate architectural judgment, migration leadership, influence without authority, and accountability — the traits that separate senior ASP.NET Core engineers from experienced individual contributors.

Tell me about the most significant architectural decision you drove on an ASP.NET Core platform. What alternatives did you reject, and how did it play out?

Why it matters: Seniors are hired for judgment; the quality of their trade-off reasoning matters more than the outcome itself.
What to listen for: Green flags: explicit alternatives with criteria (consistency, latency, Azure cost, operational load, team skills) — e.g., App Service vs Container Apps vs AKS, or gRPC vs REST vs Service Bus for an integration — a written ADR, measurable results, and honest discussion of what they would change. Red flags: resume-driven choices ('microservices on AKS because it's modern') or no measurement of outcomes.

How did you plan and execute a large migration, such as .NET Framework ASP.NET to ASP.NET Core or moving a fleet across .NET LTS versions?

Why it matters: Migrations reveal planning skill, risk management, and the ability to coordinate many teams.
What to listen for: Green flags: inventory of dependencies and blockers (System.Web usage, WCF clients, Windows-only libraries), an incremental strangler-fig approach with YARP and System.Web adapters, the .NET Upgrade Assistant or analyzers to find breaking changes, deployment-slot or canary rollouts with Application Insights comparisons, and rollback plans. Red flags: a big-bang rewrite with no rollback, or ignoring authentication and session compatibility between old and new apps.

Two teams disagree about whether a new capability should be a separate service or a module in an existing ASP.NET Core application. How do you resolve it?

Why it matters: Tests influence without authority and principled decision-making.
What to listen for: Green flags: framing the decision around domain boundaries, data ownership, deployment cadence, and team topology; considering a modular monolith with enforced module boundaries before a network hop; time-boxing a spike; documenting the decision and the criteria for revisiting it. Red flags: deciding by seniority or avoiding the conflict.

How do you grow mid-level engineers into seniors on your team?

Why it matters: A senior engineer's leverage comes from multiplying the team.
What to listen for: Green flags: delegating design ownership with guardrails, structured design reviews, pairing on incidents and performance investigations with dotnet-trace or Application Insights profiler, sponsoring internal talks or RFCs, and concrete examples of people they helped promote. Red flags: hoarding critical work, or 'they should learn on their own'.

Describe a time a production incident exposed a flaw in an architecture you designed. What did you do?

Why it matters: Checks accountability and learning culture at the leadership level.
What to listen for: Green flags: owning the flaw openly, leading a blameless post-mortem, fixing the systemic issue (e.g., adding timeouts and circuit breakers through resilience handlers, moving work behind a queue, adding bulkheads with concurrency limiters), and sharing learnings across teams. Red flags: deflecting blame onto Azure or another team, or only patching symptoms.

TESSA, the SkillSauce AI interviewer, can run a structured first-round interview built around questions like these. See how TESSA AI interviews work.

Verified Senior ASP.NET Core Technical Questions

Five HARD-tier multiple-choice questions taken verbatim from the SkillSauce ASP.NET Core question bank (it/question_bank/ASP.NET Core.json), covering inter-service communication security, large file upload streaming, middleware ordering for latency, DI lifetimes at scale, and secret management across environments. Use each as a springboard for deeper architectural follow-ups.

When deploying an ASP.NET Core application within a microservices architecture, which communication approach most effectively balances performance with security for inter-service calls in a production environment?

Hard

aUtilize SOAP over HTTPS with WS-Security
bImplement gRPC over HTTP/2 with mutual TLSCorrect
cUse standard HTTP REST API over HTTP/1.1 with JWT tokens
dImplement raw TCP sockets with custom encryption

Explanation: gRPC leverages HTTP/2 for performance and supports streaming, while mutual TLS provides robust security for service-to-service communication in microservices deployments.

Why it matters: Probes inter-service communication design: Grpc.AspNetCore with protobuf contracts over HTTP/2, and mutual TLS either through Kestrel client-certificate authentication (Microsoft.AspNetCore.Authentication.Certificate) or a service mesh on AKS. Treat the key as a springboard rather than an absolute: strong seniors also explain when REST with Entra ID client-credentials tokens is the better choice (external or browser consumers, API Management policies, simpler debugging), that every hop must support HTTP/2 end to end for gRPC, and when asynchronous messaging over Service Bus removes the temporal coupling altogether.

In a high-traffic ASP.NET Core application that handles large file uploads, which strategy is most practical to minimize memory usage and improve performance?

Hard

aUse synchronous file I/O with unbuffered streams
bBuffer entire files in memory before saving
cStream file uploads directly to storage using asynchronous I/OCorrect
dSave file data temporarily to disk and then process it

Explanation: Streaming uploads directly to storage with asynchronous I/O minimizes memory footprint and efficiently handles large files under heavy load.

Why it matters: Tests knowledge of how ASP.NET Core handles request bodies: IFormFile model binding buffers each file (spilling to a temp file on disk above 64 KB) before the action runs, while Kestrel's MaxRequestBodySize and FormOptions.MultipartBodyLengthLimit cap upload size. Seniors should describe streaming with MultipartReader and disabled form-value model binding, piping the stream straight to Azure Blob Storage asynchronously, per-endpoint [RequestSizeLimit], and — often best — issuing short-lived SAS URLs so clients upload directly to Blob Storage and the API never touches the bytes.

In an ASP.NET Core application experiencing latency issues, which middleware pipeline ordering change is most likely to yield performance improvements?

Hard

aPlace static file serving middleware before authentication when files are publicly accessibleCorrect
bPlace authentication and logging as early middleware to short-circuit requests
cInsert exception handling middleware after routing middleware
dDelay error handling middleware to the end of the pipeline

Explanation: By positioning static file serving earlier in the middleware pipeline, the application avoids unnecessary processing for publicly available content, thereby reducing latency.

Why it matters: Evaluates whether the candidate reasons about the pipeline as a cost model: UseStaticFiles short-circuits before routing, authentication, and authorization, so public assets skip token validation entirely — which is also why anything placed before authorization is public. Follow up on the rest of the recommended order (exception handler first, forwarded headers before anything that reads scheme or client IP, CORS before output caching, rate limiting after routing for endpoint-specific policies), on MapStaticAssets in .NET 9+, and on offloading static content to a CDN or Front Door.

For managing complex object lifetimes in a large-scale ASP.NET Core solution, which dependency injection lifetime configuration best prevents memory leaks and supports scalability in web applications?

Hard

aAvoid dependency injection and use service locators to manage lifetimes
bUse scoped lifetime for services that interact with the databaseCorrect
cRegister services as transient regardless of their resource usage
dRegister all services as singletons for simplicity

Explanation: Using a scoped lifetime for database-related services ensures a new instance per request, which improves resource management and reduces the risk of memory leaks.

Why it matters: Seniors should go well beyond 'scoped for the database': captive dependencies when scoped services are captured by singletons, transient IDisposable services resolved from the root provider being tracked until application shutdown (a genuine leak), turning on ValidateScopes and ValidateOnBuild in CI rather than only in Development, creating scopes with IServiceScopeFactory inside BackgroundService loops, keyed services in .NET 8, and IHttpClientFactory handler lifetimes. Option a's service locator is an anti-pattern that hides these problems.

In the context of ASP.NET Core's configuration system, which method effectively manages environment-specific settings while safeguarding sensitive production data?

Hard

aRely solely on appsettings.json for all environments
bHard-code sensitive information directly in the startup code
cUse in-memory collections for production configuration
dUse environment variables combined with user secrets in developmentCorrect

Explanation: Combining environment variables with user secrets provides a secure and flexible approach, allowing sensitive data to be protected while adapting configuration based on the environment.

Why it matters: The keyed answer is the baseline; at senior level expect the production story. User secrets are plain-text JSON outside the repository and are loaded only in Development, so production secrets belong in Azure Key Vault — via the Key Vault configuration provider with DefaultAzureCredential and a managed identity, or App Service Key Vault references — with Azure App Configuration for non-secret settings and sentinel-key refresh. Probe secret rotation without restarts, AKS workload identity with the Secrets Store CSI driver, and why connection strings should move to managed-identity authentication against Azure SQL entirely.

Need more questions for this stack? Browse sample questions by skill in the SkillSauce Question Library.

High-Touch Rejection Templates for Senior ASP.NET Core Candidates

Senior .NET candidates are often MVPs, speakers, or future hiring managers, and the community is small. Close the loop personally, acknowledge their investment, and offer a follow-up conversation.

Post-Assessment Rejection

Subject: Your Senior Backend Developer (ASP.NET) application at [Company Name]

Show template

Hi [Candidate Name], Thank you for investing an hour in our SkillSauce distributed systems assessment for the Senior Backend Developer (ASP.NET) role. We know senior candidates have limited time, and we don't take that lightly. After a careful review of your SkillSauce report by our Principal Engineer, we've decided not to proceed. The role requires immediate leadership on [e.g., event-driven consistency and multi-instance correctness], and your submission left gaps in [e.g., outbox atomicity with SaveChangesAsync / consumer idempotency under duplicate deliveries / SignalR scale-out] that we couldn't resolve in the time available. We recognize a timed exercise captures only part of your experience. We'd welcome the chance to reconnect for future senior or staff openings. Thank you again for your time and thoughtfulness. Kind regards, [Your Name] [Company Name]

Post-Interview Rejection

Subject: Thank you — Senior Backend Developer (ASP.NET) at [Company Name]

Show template

Hi [Candidate Name], Thank you for the depth and generosity you brought to our process — the system design session with [Interviewer Name] sparked a lot of discussion on our team, especially your thinking on [specific strength, e.g., sizing Azure SQL connection pools across autoscaled Container Apps replicas]. This was one of our hardest decisions, but we've chosen to move forward with a candidate whose background more closely matches our immediate priority of [specific need, e.g., leading our .NET Framework to ASP.NET Core migration]. That reflects our current needs, not a lack of capability on your part. If you're open to it, I'd value staying connected — and I'd be glad to share more detailed feedback in a short call. We hope our paths cross again. Warm regards, [Your Name] [Company Name]

Put This Guide to Work

SkillSauce tools that cover the steps above when you hire a Backend Developer (ASP.NET).

See how SkillSauce fits your hiring process

Book a demo with the team, or start a free trial.

Book a demo Start free trial

Hiring Workflow, Step by Step

Open a Job Profile for the role

Fill the candidate pool

Shortlist the strongest resumes

Test the skills the role needs

Interview with TESSA AI

Meet the shortlist

Decide together and make the offer

Company Fit: Startups, SMBs and Enterprises

Startups

SMBs

Enterprises

Junior Backend Developer (ASP.NET)

How to Hire a Junior Backend Developer (ASP.NET)

Define a Realistic Junior Scope

Source From .NET Learning Communities

Screen With a 30-Minute SkillSauce Practical Assessment

Run a 15-Minute TESSA AI Interview

Hold a 45-Minute Pair-Debugging Session

Extend an Offer With a Mentorship Plan

Pro Tips

Junior Backend Developer (ASP.NET) Job Description Template

Role Overview

First 90 Days Deliverables

Must-Have Requirements

Nice-to-Have Skills

Benefits & Mentorship

Sourcing Channels for Early-Career ASP.NET Core Talent

Job Boards

Campus Placement Cells and Referrals

Social Outreach Copy for Junior ASP.NET Core Developers

LinkedIn Post

Twitter / X Post

LinkedIn Direct Message

Email Sequence for Junior ASP.NET Core Candidates

Cold Sourcing

Interview Invite

Offer Letter

Junior ASP.NET Core SkillSauce & TESSA Assessment Blueprint

Why This Assessment Mix

Behavioral & Fundamentals Rubric for Junior ASP.NET Core Developers

Walk me through what happens to an HTTP request from the moment Kestrel receives it until your controller action's return value is written to the client as JSON.

Tell me about a bug in one of your .NET projects that took you more than a day to solve. How did you eventually find it?

When would you register a service with AddTransient, AddScoped, or AddSingleton? Give a real example of each from something you built.

Describe a time you received critical feedback on your code in a pull request. What did you change?

Verified Junior ASP.NET Core Technical Questions

You have developed a custom middleware for logging requests in your ASP.NET Core app. What is the easiest way to add this middleware into the HTTP request pipeline?

During development, you notice that a required service is not being injected into your controller. What is the most likely practical reason for this issue?

When setting up an ASP.NET Core application for production, which method should you use to efficiently capture and log errors?

You're building a versioned API using ASP.NET Core. What is the recommended way to handle API versioning in the URL structure?

An ASP.NET Core application is experiencing sporadic slow response times. As a first step in your troubleshooting process, what practical measure should you take?

Constructive Rejection Templates for Junior ASP.NET Core Candidates

Post-Assessment Rejection

Post-Interview Rejection

Mid-Level Backend Developer (ASP.NET)

How to Hire a Mid-Level Backend Developer (ASP.NET)

Scope the Role Around API Ownership

Source Engineers With Production ASP.NET Core Footprints

Administer a 45-Minute SkillSauce Performance & Security Assessment

Use a 20-Minute TESSA AI Interview for Ownership & Trade-Offs

Run a 60-Minute Live Code Review & Design Session

Close With a Competitive, Ownership-Focused Offer

Pro Tips

Mid-Level Backend Developer (ASP.NET) Job Description Template

Role Overview

First 90 Days Deliverables

Must-Have Requirements

Nice-to-Have Skills

Benefits & Mentorship

Targeted Sourcing Channels for Mid-Level ASP.NET Core Engineers

Job Boards

Employee Referrals

Social Outreach Copy for Mid-Level ASP.NET Core Engineers

LinkedIn Post

Twitter / X Post

LinkedIn Direct Message

Email Sequence for Mid-Level ASP.NET Core Candidates

Cold Sourcing

Interview Invite

Offer Letter