Redis is a good fit when the design needs low-latency shared state: rate limiters, leaderboards, sessions, cache entries, and small pieces of real-time application state.

Redis delivers low latency by keeping the working set in memory, and its data structures (lists, sets, sorted sets, streams, hashes) let you model more than plain key-value lookups.

The interview answer should not stop at "Redis is fast." Explain when Redis fits, which data structure matches the access pattern, and what failure or durability trade-off you are accepting.

For interviews, focus on data structure selection, persistence trade-offs, replication, clustering, cache patterns, rate limiting, and when Redis should not be the source of truth.