Top 100+ Most Asked Redis Interview Questions

A comprehensive guide covering Redis fundamentals, data types, persistence, performance, scaling, and advanced features.

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1.What is Redis?

2.What is Redis and why is it used?

3.What is an in-memory Database?

4.Is Redis just a cache?

5.How does Redis differ from traditional databases like MySQL?

6.Why would you use Redis over Memcached?

7.When to use Redis over MongoDB?

8.What's the advantage of Redis vs using memory?

9.What are the Redis gotchas?

10.Describe a scenario where Redis is not the appropriate choice.

11.What are Redis data types and their use cases?

12.What is the Redis String data-type?

13.Explain the SET & GET commands.

14.What is the Redis List data-type?

15.When to use Redis Lists data type?

16.Explain Redis List operations.

17.Explain Blocking operations on lists.

18.What is the Redis SET data-type?

19.When to use Redis Sets?

20.Explain Redis SET operations.

21.Explain SINTER & SUNION.

22.Explain SUNIONSTORE & SINTERSTORE.

23.What is the Redis Hashes data-type?

24.What are Redis hashes?

25.When to use Redis Hashes data type?

26.Explain HASH data-type operations.

27.Explain Redis Sorted sets.

28.Explain a use case for Sorted Set in Redis.

29.Explain Redis Sorted Set operations.

30.What are the underlying data structures used for Redis?

31.Explain how Redis uses keys.

32.Is there a way to check if a key already exists in a Redis list?

33.What is Key Eviction, and how is it configured?

34.How does Redis manage memory?

35.What happens if Redis runs out of memory?

36.Discuss the limitations of Redis regarding data size and type.

37.Does Redis persist data?

38.How do you ensure persistence in Redis?

39.Isn't the Redis data lost if there's a system crash?

40.How does Redis achieve persistence by Snapshotting?

41.What is RDB persistence?

42.How does Redis achieve persistence by AOF (Append-only files)?

43.What is AOF persistence in Redis?

44.Files will keep on growing as long as AOF is executed. Won't it consume more memory? What is the solution provided by Redis?

45.What are the main differences between RDB and AOF?

46.RDB and AOF, which one should I use?

47.What is the impact of persistence settings on Redis performance?

48.Is Redis a durable datastore ('D' from ACID)?

49.Explain the concept of Redis transactions.

50.Does Redis support transactions?

51.Why does Redis not support roll backs?

52.Can Redis be used in a multi-threaded application, and how does it handle concurrency?

53.How does Redis handle multiple threads (from different clients) updating the same data structure?

54.What is Pipelining in Redis and when to use one?

55.Explain the use of Pipelining in Redis.

56.How are Redis pipelining and transaction different?

57.How can I exploit multiple CPU/cores for Redis?

58.What do the terms 'CPU bound' and 'I/O bound' mean in context of Redis?

59.How do you optimize Redis for high read volumes?

60.How much faster is Redis than MongoDB?

61.What is pub/sub in Redis?

62.How does Redis Pub/Sub work?

63.What are the use cases for Redis Pub/Sub?

64.How can you scale Redis?

65.What is Redis clustering, and why is it important?

66.What is the difference between Redis replication and sharding?

67.Describe Redis Sentinel and its role.

68.What is Redis Sentinel used for?

69.What is Redis Cluster?

70.How does Redis replication work?

71.How do you handle caching in a distributed environment using Redis?

72.What are common caching patterns in Redis?

73.What is cache invalidation and how do you handle it in Redis?

74.What is the difference between cache-aside and write-through patterns?

75.Explain how Lua scripting is used in Redis.

76.What are Redis Modules, and how do they enhance functionality?

77.How would you efficiently store JSON in Redis?

78.What is RedisJSON?

79.What is RedisGraph?

80.What is RedisSearch?

81.How can you monitor and debug Redis performance issues?

82.What Redis commands help with monitoring?

83.What is the INFO command in Redis?

84.What is the MONITOR command?

85.How do you identify slow queries in Redis?

86.What security features does Redis offer?

87.How do you secure a Redis instance?

88.Does Redis support authentication?

89.What is Redis ACL (Access Control List)?

90.What is the EXPIRE command?

91.What is the TTL command?

92.What is the DEL command?

93.What is the EXISTS command?

94.What is the SCAN command and why is it better than KEYS?

95.What is the difference between FLUSHDB and FLUSHALL?

96.What are common use cases for Redis?

97.When would you use Redis as a primary database?

98.How do you implement rate limiting with Redis?

99.How do you implement session management with Redis?

100.How do you implement a leaderboard with Redis?