Comprehensive Collection of Backend Interview Questions for Alibaba Cloud, Meituan, and JD

Alibaba Cloud Interview Questions

1. What are the drawbacks of ThreadLocal, and what issues arise when using ThreadLocal in a thread pool?

2. Explain the class loading mechanism and the purpose of the parent‑delegation model; how can it be broken?

3. For a system handling 1 million QPS, what aspects would you consider in its design?

4. Which design patterns do you use frequently?

5. Are you familiar with the Reactive programming model?

6. Which distributed technologies have you used, and do you understand their underlying implementations?

7. What are the operating principles of the various Spring Cloud components?

8. What are the implementation principles of TreeMap and TreeSet?

9. What is the difference between Array and ArrayList?

10. What are the JVM memory areas and their purposes?

11. Describe the JVM heap structure, the conditions that trigger garbage collection, and the types of GC that may occur.

12. How do you optimize database performance?

13. What are the differences between synchronized and Lock?

14. Have you used reverse proxy servers? What are they used for, and what parameters does Nginx provide for load balancing?

15. Explain the implementation principles of the messaging middleware you are familiar with and its advantages over other message queues.

16. What is the difference between Poll and ePool?

17. Compare BIO and NIO.

18. Write a compilable program: given a list representing the number of instances in a cluster and a batch size, evenly deploy applications across all instances.

Meituan Interview Questions

1. What are the MySQL storage engine types, their differences, and typical use cases?

2. List MySQL transaction isolation levels and illustrate each with examples.

3. What types of database locks exist and how do they differ?

4. How do you tune and optimize MySQL SQL statements; which parameters are most important?

5. What index types does MySQL provide and how do they differ?

6. Explain pessimistic and optimistic locks, their characteristics, and scenarios.

7. Describe row‑level and table‑level locks; for the statement update t1 set a = xx for update, is it a row‑level or table‑level lock and why?

8. How do you use MySQL and Redis in master‑slave and high‑availability setups, and in what scenarios do you typically use Redis?

9. Compare synchronized and volatile, and give appropriate usage scenarios.

10. Have you encountered deadlocks in projects? How did you resolve them?

11. Discuss your understanding of JMM, CAS, and AQS, including the ABA problem in CAS and its mitigation.

12. Explain the flow of single sign‑on and the OAuth2 protocol and their differences.

13. Which design patterns do you commonly use? Provide class diagrams and explanations.

14. What are the core object‑oriented design principles?

15. Why use getters and setters instead of exposing fields directly?

16. What runtime data areas does the JVM contain?

17. What are the GC roots in the JVM?

18. How do you tune JVM garbage collection?

19. How would you implement rate limiting? List common algorithms and their use cases.

20. Which Guava classes have you used and how well do you understand their internal implementations?

21. In a distributed flash‑sale scenario without a distributed lock, using only Guava and JDK utilities, how would you implement the solution?

22. Explain Spring AOP and its underlying implementation.

23. What are the core classes of Spring?

24. What are Inversion of Control (IoC) and Dependency Injection (DI) in Spring?

25. How do Spring‑managed beans differ from manually instantiated objects, and what problems arise when too many beans are configured?

26. What isolation modes does Hystrix provide and how does a circuit breaker work?

27. Describe the processing flow of Spring Cloud Zuul.

28. How does Dubbo handle cluster fault tolerance?

29. Explain the implementation principle of the Dubbo registry.

30. Compare Dubbo and Spring Cloud, highlighting their advantages and disadvantages.

31. Discuss your understanding of BIO, NIO, and Netty and their underlying implementations.

32. Explain the reactor pattern.

33. What are Docker and Kubernetes used for? Provide a brief description.

JD Interview Questions

1. List the garbage collectors and their algorithms, and indicate suitable business scenarios for each.

2. Describe concurrency models/patterns you know (e.g., producer‑consumer) and where you have applied them.

3. How can a main thread wait for multiple child threads to finish in Java? List the possible implementations.

4. Enumerate inter‑system communication methods, their characteristics, and which you have used.

5. Explain the data structure of HashMap and the modifications made in ConcurrentHashMap.

6. Summarize Java’s class loading mechanism and answer whether two identical classes can exist in one JVM.

7. List the open‑source frameworks you have used and your proficiency with each.

8. If two public methods M1 and M2 in class C have aspects applied, and M1 calls M2, describe the aspect execution order when M1 is invoked.

9. What types of indexes exist in relational databases and what data structures store them?

10. Given a table T with columns A, B, C, D, an index on B (idx1) and a composite index on A+B+C (idx2), which index will be used for select * from T where B=? and A=? and C=? and why?

11. Discuss the types and granularity of relational database queries.

12. List the transaction isolation levels for relational databases.

13. Provide common optimization strategies for relational databases.

14. Explain Spring transaction propagation types and their implementation.

15. How would you handle dynamic shard addition in a sharded database, including data migration?

16. Summarize the principles of distributed transactions.

17. Write a Java program to count duplicate log entries in a 1‑TB log file.

18. Implement an LRU cache in Java.

19. List common Linux commands for networking, file/text processing, scheduling, and disk management.

20. Summarize design principles you are familiar with and their meanings.

21. Describe design patterns you know and where you have applied them in projects.

22. Explain the CAP theorem and BASE theory.

23. Design a ticket‑booking system that ensures first‑come‑first‑served ordering, configurable total quantity, and persistent purchase records; provide domain model, core module division, and deployment diagram.

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