Redis

Redis is an in-memory key-value database for developers and platform teams that need caching, sessions and messaging, hosted or self-managed.

Redis holds its data in memory, which is why caches, session stores, message queues and leaderboards are built on it. It also serves real-time decisioning and vector search workloads. Redis Ltd. makes and sells it as an independent company, with Francisco Partners as a financial investor. The same product ships as Redis Cloud, as Redis Software for on-premises use and as an Open Source edition. Data lives in native types: strings, hashes, lists, sets, sorted sets, streams and JSON documents. Keys expire on a TTL, and eviction policies such as allkeys-lru and allkeys-lfu apply when memory fills. Persistence comes from RDB snapshots and the append-only file. Redis Search indexes JSON and hash fields so queries can go beyond key lookups. Pub/sub channels handle fan-out messaging, and streams with consumer groups spread entries across workers. Lua scripts and Redis Functions run atomically on the server. Redis Sentinel promotes a replica when a primary fails, and Redis Cluster shards the keyspace across nodes. Active-Active databases accept writes in several regions. Redis Flex extends a database across RAM and SSD. With client-side caching, the server tracks the keys a client has read and sends an invalidation message when a key changes. The redis-py, Jedis, node-redis and go-redis client libraries support it. Backend developers use Redis as a cache in front of a relational database or as a session store for web apps. Platform teams run the Open Source edition or Redis Software themselves, while teams that prefer a managed service choose Redis Cloud, which has Free, Essentials and Pro tiers. Global apps that need writes in several regions use Active-Active on Pro or Redis Software. Redis Software is quoted through sales. Redis also acts as a message layer between services, a store for leaderboards built on sorted sets, and a low-latency lookup layer fed by Redis Data Integration from upstream databases and warehouses. Redis Insight is a graphical client that browses keys and manages streams and consumer groups.