.NET Interview Preparation
Prepare for .NET developer interviews — common questions, system design challenges, coding exercises, and strategies for landing senior roles.
50 min•By Priygop Team•Last updated: Feb 2026
Core .NET Interview Topics
- CLR & Runtime: How does garbage collection work? What are value types vs reference types? How does the JIT compiler optimize code? Stack vs heap allocation
- Async/Await: Explain the state machine generated by async/await. What's the difference between Task and ValueTask? How does ConfigureAwait work?
- Dependency Injection: Explain Transient, Scoped, and Singleton lifetimes. What happens if you inject a Scoped service into a Singleton? (Captive dependency)
- Entity Framework Core: Change tracking, lazy vs eager loading, N+1 problem, compiled queries, migrations strategy, DbContext lifetime in ASP.NET Core
- LINQ: Deferred execution vs immediate execution. IEnumerable vs IQueryable (in-memory vs SQL translation). Performance implications of materializing queries
- Middleware Pipeline: How does the ASP.NET Core middleware pipeline work? What's the difference between Map, Use, and Run? How does routing work?
System Design Questions
- Design a URL Shortener: Database storage, hash generation (Base62), collision handling, analytics tracking, caching hot URLs, rate limiting
- Design a Chat System: WebSocket/SignalR, message persistence, presence tracking, group management, message delivery guarantees, offline message queue
- Design an E-commerce Backend: Order service, inventory management, payment processing (Saga), product catalog, search (Elasticsearch), recommendations
- Design a Notification System: Multi-channel (push, email, SMS, in-app), template management, user preferences, rate limiting, delivery tracking
- Design a Rate Limiter: Token bucket vs sliding window, distributed rate limiting with Redis, per-user vs per-IP, response headers (X-RateLimit-Remaining)
- Key Principles: Start with requirements, estimate scale, design high-level components, deep-dive into critical paths, discuss trade-offs, propose monitoring