Redis - Redis is an open source in-memory data structure project implementing a distributed, in-memory key-value database with optional durability.
Apache Ignite - high-performance, integrated and distributed in-memory platform for computing and transacting on...
KeyDB - KeyDB is fast NoSQL database with full compatibility for Redis APIs, clients, and modules.
eAccelerator - eAccelerator is a free open-source PHP accelerator & optimizer.
memcached - High-performance, distributed memory object caching system
Skytable - Skytable is a free and open-source realtime NoSQL database that aims to provide flexible data modelling at scale.