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Java Backend Developer Interview

CORE JAVA: 1. HashMap internal working. What happens when a bucket turns into a tree. 2. HashMap vs ConcurrentHash Map vs Hashtable. 3. equals and hashCode contract. Break it and watch your Set duplicate. 4. Whv is String immutable 5. Comparable vs Comparator 6. Checked vs unchecked exceptions. 7. Can you override a static method 8. trv with resources. 9. Which Java 8, 11 and 17 features you have actually shipped STREAMS: 10. Find duplicate strings in a list using Streams. 11.map vs flatMap. 12. Sort a map bv value 13. Optional. Where it actually saves you. MULTITHREADING: 14. Runnable vs Callable 15. ExecutorService and how vou size a thread pool 16. synchronized vs ReentrantLock. 17. volatile vs AtomicInteger. 18. Deadlock. How you detect it in a running JVM SPRING BOOT: 19. Spring vs Spring Boot. 20. How autoconfiguration works. 21. Component vs Service vs Repository 22. How dependency iniection resolves at startup. 23. Transactional. What rolls back on a checked exception 24. ControllerAdvice and global exception handling 25. Spring Security and the JWT flow. MICROSERVICE: 26. How two services find each other 27. What an API gatewav actually does. 28. Circuit breaker. Why retries alone make the outage worse. 29. Tracing one request across five services SQLAND HIBERNATE: 30. When an index hurts instead of helps. 31. Find duplicate rows. 32. Second highest salary without LIMIT. 33. N plus 1 problem. How you kill it. 34. Lazy vs eager loading. CODING ROUND: 35. Move all zeroes to the end. 36. Check if two strings are anagrams. 37. Longest common prefix. 38. Missing number in a consecutive array. MANAGERIAL: 39. Draw your project architecture end to end. 40. A production bug you owned. 41. Notice period and relocation.