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Top 50 Java Backend Debugging & Production Scenario Questions (3–10 YOE)
Java Interview Questions
1. API is slow in production — where do you start debugging?
2. High CPU usage after deployment — what will you check?
3. Memory usage keeps increasing — possible causes?
4. How do you identify memory leaks in Java?
5. How do you analyze heap dump?
6. How do you analyze thread dump?
7. What if DB queries suddenly become slow?
8. How do you identify missing indexes?
9. How to debug connection pool exhaustion?
10. What happens if thread pool is exhausted?
11. How do you handle high latency in APIs?
12. What if one microservice is slowing entire system?
13. How to debug timeout issues?
14. How do you handle cascading failures?
15. What is circuit breaker real use case?
16. How do you debug Kafka consumer lag?
17. What if messages are duplicated?
18. How to handle idempotency in retries?
19. What if logs are not sufficient?
20. How to improve observability?
21. How do you implement distributed tracing?
22. What metrics do you monitor in production?
23. How to detect slow endpoints?
24. What is p95 vs p99 latency?
25. How to debug GC pauses?
26. What causes OutOfMemoryError?
27. How to fix memory fragmentation?
28. How to handle traffic spikes?
29. How to scale application quickly?
30. What is autoscaling strategy?
31. What if deployment breaks production?
32. How do you rollback safely?
33. What is blue-green deployment?
34. How to validate canary release?
35. How to handle config issues in prod?
36. What if cache is not working?
37. Cache miss vs cache stampede?
38…
