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...
memcached - High-performance, distributed memory object caching system
Varnish - High-performance HTTP accelerator
Bluzelle Decentralized DB - Bluzelle is a decentralized database powered by PBFT Consensus Engine.
MongoDB - MongoDB (from "humongous") is a scalable, high-performance NoSQL database.