100 Scenario-Based .NET Interview Questions 🚀

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Introduction

Scenario-based interview questions are designed to test a developer’s real-world problem-solving skills, not just theoretical knowledge. For senior .NET developers, leads, and architects, these questions often revolve around production issues, performance bottlenecks, microservices, cloud deployments, and team leadership. This blog organizes 100 commonly asked scenario-based questions into structured sections, making it easier to study and prepare.

1. Production / Performance Issues

  1. Your API is suddenly slow in production. How do you troubleshoot?

  2. CPU usage is 100% on server. What do you check first?

  3. Memory usage keeps increasing. How do you identify memory leak?

  4. SQL query is slow only in production. What will you do?

  5. Application works locally but slow on server. Why?

  6. How do you find thread blocking issue?

  7. How do you identify deadlock in SQL Server?

  8. Response time increased after deployment. What do you check?

  9. App crashes under heavy load. How do you fix it?

  10. How do you improve API response time?

2. Database Issues

  1. Database deadlock happening frequently. How to resolve?

  2. Stored procedure suddenly became slow. Why?

  3. Index fragmentation issue. What will you do?

  4. Table has millions of records; query is slow. Optimize it.

  5. Duplicate records inserted. How to prevent?

  6. Transaction rollback issue in production.

  7. Connection pool exhausted. Why?

  8. Database server down. What is your DR plan?

  9. Data inconsistency issue across services.

  10. How to archive old data?

3. Microservices

  1. One microservice is down; how system should behave?

  2. Service-to-service communication failing.

  3. How to handle distributed transaction?

  4. Event is published twice. How to avoid duplicate processing?

  5. Message stuck in queue. What do you do?

  6. Consumer not processing messages.

  7. How to retry failed messages?

  8. Service discovery not working.

  9. Circuit breaker open frequently.

  10. API Gateway is failing.

4. Security

  1. JWT token expired issue in production.

  2. User accesses unauthorized API. How to fix?

  3. API under DDOS attack.

  4. SQL Injection vulnerability found.

  5. XSS issue reported.

  6. Password stored insecurely.

  7. Secret key exposed in code.

  8. Internal service exposed publicly.

  9. SSL certificate expired.

  10. API key leaked.

5. Azure / Cloud

  1. Azure App Service is slow.

  2. Azure Function timeout issue.

  3. Azure Service Bus messages not processed.

  4. Azure SQL DTU/CPU high.

  5. Azure storage unavailable.

  6. App Service deployment failed.

  7. CI/CD pipeline failed.

  8. AKS pod restarting continuously.

  9. Container crash issue.

  10. How to reduce Azure cost?

6. API / Integration

  1. Third-party API is slow.

  2. Third-party API is down.

  3. API returning 500 error randomly.

  4. API versioning issue.

  5. CORS issue in production.

  6. File upload fails for large files.

  7. API timeout issue.

  8. Duplicate API request issue.

  9. Payment gateway callback issue.

  10. External webhook retry issue.

7. Logging / Monitoring

  1. Logs are not coming in production.

  2. Need to trace request across microservices.

  3. How to monitor distributed system?

  4. How to identify root cause from logs?

  5. No alerts configured; production failed.

8. Deployment / DevOps

  1. Deployment failed in production.

  2. Rollback deployment quickly?

  3. Blue-green deployment issue.

  4. Environment variable missing after deployment.

  5. IIS app pool stopped.

9. Angular / Frontend

  1. Angular app slow in browser.

  2. API call repeated multiple times.

  3. Lazy loading issue.

  4. Build failing in production.

  5. Memory leak in Angular.

10. Concurrency / Async

  1. Race condition issue.

  2. Deadlock in async code.

  3. Task not awaited issue.

  4. Parallel API calls causing issue.

  5. Shared resource issue.

11. Architecture / Design

  1. Design scalable e-commerce system.

  2. Design payment system.

  3. Design notification service.

  4. Design chat application.

  5. Design URL shortener.

12. Leadership / Team Handling

  1. Junior developer deployed bad code.

  2. Conflict between team members.

  3. Production issue at midnight.

  4. Deadline very close.

  5. Requirement changed at last moment.

13. Real-world Project

  1. Biggest challenge you faced in project?

  2. How did you optimize system performance?

  3. How did you migrate monolith to microservices?

  4. How did you handle legacy code?

  5. How did you improve security?

14. Testing / Quality

  1. Bug found in production.

  2. Unit tests failing in pipeline.

  3. Integration test issue.

  4. Production issue not reproducible locally.

  5. How do you ensure code quality?

Conclusion

These 100 scenario-based questions cover the breadth of real-world challenges faced by senior .NET developers, leads, and architects. From troubleshooting production issues to designing scalable systems and handling team dynamics, this list serves as a comprehensive guide for interview preparation. By preparing answers with your own project examples, you’ll not only be ready for interviews but also demonstrate practical expertise in solving complex problems.



This was part of Interview Preparation With Bipin — Let’s Crack It!

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