MySQL - The world's most popular open source database
Parse - Build applications faster with object and file storage, user authentication, push notifications, dashboard and more out of the box.
PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
SQLite - SQLite Home Page
AnyPresence - AnyPresence is an Enterprise Backend as a Service for mobile app development and API augmentation.