What it does
FerretDB translates queries sent over the MongoDB 5.0+ wire protocol into SQL for PostgreSQL with the DocumentDB extension. Applications can connect through MongoDB-compatible drivers while FerretDB and its database backend run as software you deploy. The project documents a growing set of compatible commands and known differences, so check the operations your application relies on before planning a migration.
Evaluate the compatibility layer
FerretDB's installation guide links an evaluation image that bundles FerretDB, PostgreSQL with the DocumentDB extension, and MongoDB Shell. A developer can use the bundled setup to see how a MongoDB-compatible client talks to the proxy and reaches the PostgreSQL-backed data store. This is a documented evaluation path, not a command run or a production deployment for this listing.
An illustrative migration check is to take a small test service that already uses a MongoDB driver, point it at a separate FerretDB evaluation instance, and run the application's own query tests. Then compare any unsupported commands or behavior against FerretDB's compatibility documentation. The project describes direct replacement for MongoDB 5.0+ applications as a possible use, not a guarantee of full feature equivalence.
Do not treat the bundled evaluation image as durable production storage: the project notes that its container data is lost when the container shuts down. A production design needs a deliberately configured database backend and persistent storage. The FerretDB server is published under Apache 2.0; any separate cloud hosting choice has its own terms and costs.
Strengths
- Accepts connections through MongoDB-compatible drivers and wire protocol.
- Uses PostgreSQL with the DocumentDB extension as its database engine.
- The project publishes an evaluation setup for trying the compatibility layer.
Watch out for
- MongoDB compatibility is still evolving, so application-specific operators need checking.
- The bundled evaluation image is not a production storage configuration and does not preserve data after shutdown.
Best for
- Evaluating a PostgreSQL-backed alternative for applications using supported MongoDB operations
- Testing MongoDB-compatible drivers against a self-managed document database proxy
Sources
- Introduction | FerretDB (Oct 26, 2026)
- Installation | FerretDB (Oct 26, 2026)
- FerretDB official repository (Oct 26, 2026)
- FerretDB LICENSE (Oct 26, 2026)