CouchBase - Document-Oriented NoSQL Database
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.
memcached - High-performance, distributed memory object caching system
Dragonfly DB - Dragonfly - Scalable in-memory datastore made simple
Aerospike - Aerospike is a high-performing NoSQL database supporting high transaction volumes with low latency.