Redis - Redis is an open source in-memory data structure project implementing a distributed, in-memory key-value database with optional durability.
KeyDB - KeyDB is fast NoSQL database with full compatibility for Redis APIs, clients, and modules.
Hazelcast - Clustering and highly scalable data distribution platform for Java
Dragonfly DB - Dragonfly - Scalable in-memory datastore made simple
Aerospike - Aerospike is a high-performing NoSQL database supporting high transaction volumes with low latency.
MongoDB - MongoDB (from "humongous") is a scalable, high-performance NoSQL database.