MongoDB - MongoDB (from "humongous") is a scalable, high-performance NoSQL database.
MySQL - The world's most popular open source database
PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
SQLite - SQLite Home Page
Apache Solr - Solr is an open source enterprise search server based on Lucene search library, with XML/HTTP and...