Redis

Redis is an in-memory data structure store used as a cache, message broker, and database. Its sub-millisecond latency makes it essential for session management, real-time leaderboards, rate limiting, pub/sub messaging, and caching layers in modern applications. Redis supports rich data structures (strings, hashes, sets, sorted sets, streams) and features like Lua scripting, transactions, and cluster mode. Redis Stack adds JSON, search, time series, and graph capabilities.