FerretDB (formerly MangoDB) is an open-source proxy, which converts MongoDB wire protocol queries to SQL, and uses PostgreSQL as a database engine.
Cost / License
- Free
- Open Source (Apache-2.0)
Platforms
- Mac
- Windows
- Linux
- Online
- Self-Hosted
MongoDB is described as 'Document database with the scalability and flexibility that you want with the querying and indexing that you need' and is a very popular relational database in the development category. There are more than 100 alternatives to MongoDB for a variety of platforms, including Linux, Windows, Mac, Self-Hosted and Web-based apps. The best MongoDB alternative is PostgreSQL, which is both free and Open Source. Other great apps like MongoDB are SQLite, MySQL Community Edition, MariaDB and Redis.
FerretDB (formerly MangoDB) is an open-source proxy, which converts MongoDB wire protocol queries to SQL, and uses PostgreSQL as a database engine.

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I like it because it is tries to build MongoDB in open-source!