# Redis Redis (Remote Dictionary Server) is an open-source, in-memory data structure store used as a database, cache, message broker, and streaming engine. Created by [[Salvatore Sanfilippo]] in 2009. Delivers sub-millisecond response times by keeping data in memory. ## Data structures - Strings, Hashes, Lists, Sets, Sorted Sets - Bitmaps, HyperLogLogs, Geospatial indexes - Streams - Vector sets (beta): for semantic similarity search and RAG ## Key features - In-memory storage with optional disk persistence (RDB snapshots or AOF log) - Pub/Sub messaging - Lua scripting - Transactions - Replication and high availability (Redis Sentinel) - Clustering for horizontal scaling - Redis Query Engine: full-text search, vector search, geospatial queries, aggregations - TTL-based key expiration ## Common use cases - Caching (database query results, API responses, sessions) - Session management - Real-time analytics and leaderboards - Rate limiting - Task/job queues - Pub/Sub messaging - AI integration: semantic caching, LLM memory, RAG ## Managed services - Redis Cloud - AWS ElastiCache - Azure Cache for Redis - Google Memorystore - Upstash (serverless Redis) ## References - Website: https://redis.io - Documentation: https://redis.io/docs - Source code: https://github.com/redis/redis ## Related - [[Salvatore Sanfilippo]] - [[PostgreSQL]]