Hazelcast - Clustering and highly scalable data distribution platform for Java
MySQL - The world's most popular open source database
Apache Storm - Apache Storm is a free and open source distributed realtime computation system.
PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
Redis - Redis is an open source in-memory data structure project implementing a distributed, in-memory key-value database with optional durability.
SQLite - SQLite Home Page