Redis

Redis is an open source (BSD licensed), in-memory data structure store used as a database, cache, message broker, and streaming engine. Redis provides data structures such as strings, hashes, lists, sets, sorted sets with range queries, bitmaps, hyperloglogs, geospatial indexes, and streams. Redis has built-in replication and different levels of on-disk persistence and provides high availability via Redis Sentinel and automatic partitioning with Redis Cluster. 

To achieve top performance, Redis works with an in-memory dataset. Depending on your use case, Redis can persist your data either by periodically dumping the dataset to disk or by appending each command to a disk-based log. You can also disable persistence if you just need a feature-rich, networked, in-memory cache. 

Redis supports asynchronous replication, with fast non-blocking synchronization and auto-reconnection with partial resynchronization on net split. 

Redis also includes: 

• Transactions 
• Pub/Sub 
• Lua scripting 
• Keys with a limited time-to-live 

• LRU eviction of keys 
• Automatic failover 

You can use Redis from most programming languages.