What are some alternatives?
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
Microsoft SQL Server - Microsoft Azure is an open, flexible, enterprise-grade cloud computing platform. Move faster, do more, and save money with IaaS + PaaS. Try for FREE.
CouchDB - HTTP + JSON document database with Map Reduce views and peer-based replication
MariaDB - An enhanced, drop-in replacement for MySQL