FerretDB
Truly open-source MongoDB alternative that runs on PostgreSQL.
About
FerretDB is an Apache 2.0 licensed proxy that speaks the MongoDB wire protocol and translates queries to SQL, storing data in PostgreSQL (with the DocumentDB extension for a native BSON type and vector search) or SQLite. It exists because MongoDB's 2018 move from AGPL to the SSPL pushed organizations seeking a genuinely open-source document database toward an alternative. Version 2.0 reached GA in March 2025 as a production-ready drop-in replacement for most MongoDB workloads, with existing drivers, URIs and aggregation pipelines working unchanged.
FerretDB launched a managed FerretDB Cloud service in August 2025, positioning it as MongoDB Atlas without the lock-in. For AI stacks already standardized on Postgres (including pgvector for embeddings), FerretDB lets document workloads and vector workloads share one database. Compatibility is broad but not total, so migration testing is still required for exotic workloads.
What it can do
- MongoDB 5.0+ wire-protocol compatibility on a Postgres backend
- Apache 2.0 license with no SSPL restrictions
- Native BSON type and vector search via the DocumentDB extension
- Built-in Data API for HTTP-based access without drivers
Setup
Run the Docker image against a Postgres backend, or sign up for FerretDB Cloud.
Prerequisites
PostgreSQL for the backend (or SQLite for local use); MongoDB drivers work as-is.
Use cases
Works with
Trust score — 8/10
Scored 8/10 (verified tier, metrics-v1). Evidence: Verified via vendor site/docs/GitHub and reputable coverage, wave 89; Trending score 78/100 from researcher assessment.
Sources
Every fact above was checked against these sources. Where a claim comes from the provider and couldn't be independently verified, the text says so.