MySQL - The world's most popular open source database
Raygun - Raygun gives developers meaningful insights into problems affecting their applications. Discover issues - Understand the problem - Fix things faster.
PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
Sentry.io - From error tracking to performance monitoring, developers can see what actually matters, solve quicker, and learn continuously about their applications - from the frontend to the backend.
SQLite - SQLite Home Page
Kafka - Apache Kafka is publish-subscribe messaging rethought as a distributed commit log.