Top 50 Redis Interview Questions & Answers (2026)

01 What is Redis? 02 How is Redis different from a traditional disk-based database? 03 What are the five core Redis data types? 04 What do the SET and GET commands do in Redis? 05 How does TTL (Time-To-Live) work in Redis? 06 What is the difference between Redis and Memcached? 07 What are the Redis persistence options (RDB and AOF)? 08 What is Redis Pub/Sub? 09 What are common real-world use cases for Redis? 10 What is Redis pipelining? 11 What does it mean that Redis operations are atomic? 12 What are the INCR and DECR commands in Redis? 13 What are LPUSH, RPUSH, LPOP, and RPOP in Redis? 14 What are SADD and SMEMBERS in Redis? 15 What are ZADD and ZRANGE in Redis? 16 What are HSET and HGET in Redis? 17 What are Redis SELECT databases? 18 How does Redis AUTH work? 19 What does FLUSHDB do in Redis? 20 What does the Redis INFO command return?

01 What is Redis Cluster and how does it shard data? 02 What is the difference between Redis Sentinel and Redis Cluster? 03 How do MULTI and EXEC work in Redis transactions? 04 What is WATCH and optimistic locking in Redis? 05 What is Lua scripting in Redis and when should you use it? 06 What are Redis eviction policies? 07 What is HyperLogLog in Redis? 08 What are Redis Streams? 09 What are Redis Geospatial commands? 10 What is RedisBloom (Bloom Filter in Redis)? 11 How do you implement rate limiting in Redis? 12 How does distributed locking work in Redis? 13 What is the cache-aside pattern vs write-through caching? 14 How does Redis replication work? 15 What is the Redis slow log? 16 What is OBJECT ENCODING in Redis? 17 What are Redis keyspace notifications? 18 What are CLIENT commands in Redis? 19 What is CLIENT TRACKING in Redis (client-side caching)? 20 How do you work around cross-slot transaction limitations in Redis Cluster?

01 How does Redis Cluster sharding and the hash slot algorithm work in detail? 02 What is consistent hashing and how does it compare to Redis Cluster's approach? 03 What is memory optimization in Redis (ziplist, listpack, and encoding thresholds)? 04 How does AOF rewrite work and how does it compare to RDB performance? 05 What are Redis Functions (replacing Lua scripts in Redis 7+)? 06 What is Redis Stack and what does it add to vanilla Redis? 07 What are large key anti-patterns in Redis and how do you fix them? 08 What is CRDT support in Redis and how does it relate to Active-Active geo-distribution? 09 How do you optimize Redis memory usage for a large-scale deployment? 10 How does Redis handle high availability in production and what are the failure modes to understand?