Redis

Redis is an open source (BSD licensed), in-memory data structure store, used as a database, cache and message broker. |
It supports data structures such as strings, hashes, lists, sets, sorted sets with range queries, bitmaps, hyperloglogs, geospatial indexes with radius queries and streams. |
Redis has built-in replication, Lua scripting, LRU eviction, transactions and different levels of on-disk persistence, and provides high availability via Redis Sentinel and automatic partitioning with Redis Cluster. |
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Check out https://redis.io/ for more information.