1. Redis is an open source in-memory data structure project implementing a distributed, in-memory key-value database with optional durability.

  2. Clustering and highly scalable data distribution platform for Java

  3. Aerospike is a high-performing NoSQL database supporting high transaction volumes with low latency.

  4. Database for real-time transactions and analytics.

  5. In-memory relational DBMS capable of supporting millions of database operations per second

  6. High performance, in-memory storage engine for time series data (by Facebook)