PostgreSQL vs FerretDB
Both are alternatives to MongoDB Atlas. Here's how they stack up — verified facts, no spin.
Also searched as FerretDB vs PostgreSQL — same comparison, one verdict.
PostgreSQL and FerretDB are closely matched on ownership (98 vs 95) — this one comes down to pricing and to which trade-offs below you can live with.
PostgreSQL
TOP PICKThe default answer, and JSONB means you may not need a document store.
Postgres is the most capable open database in general use and the one most teams should reach for first. The detail that matters on this page: JSONB gives you schemaless document storage with indexing and rich querying inside a relational database, so you can hold documents where they suit and use joins, transactions and constraints everywhere else. Add pgvector for embeddings and full-text search built in, and a large share of MongoDB deployments turn out to be Postgres deployments that took a detour. PostgreSQL Licence — permissive, foundation-governed, and not going to change.
FerretDB
MongoDB's wire protocol, speaking to Postgres underneath.
FerretDB implements the MongoDB wire protocol on top of Postgres, so an existing application keeps its drivers, its queries and its code while the data lives in an open relational database under a licence nobody will change. Apache-2.0, around 11k stars. It is the most surgical exit in this comparison: for the common case of a team using MongoDB as a straightforward document store, it is close to a drop-in. Compatibility is good rather than total — the exotic aggregation stages and MongoDB-specific features are where it stops.
Side by side
10 points of comparison, every one read from a verified field. Green marks the side that wins a row outright. A dash means we do not hold that fact — never that it is zero.
| PostgreSQL | FerretDB | |
|---|---|---|
| Sovereignty ScoreOur transparent 0–100 composite for data ownership and exit cost. | 98 | 95 |
| Open source | Yes | Yes |
| Self-hostable | Yes | Yes |
| Local-first data | Yes | Yes |
| License | PostgreSQL License (permissive) | Apache-2.0 |
| Pricing | Free and open source. Managed options exist from every cloud, usually cheaper than Atlas. | Free and open source. You run it alongside your own Postgres. |
| RAM to run it wellThe figure that actually matters, not the vendor's minimum. | 4 GB for a real application database | — |
| Realistic running costWhat the box costs each month if you run it yourself. | $24–48/mo for a 4–8 GB instance, against managed Postgres at 2–3× that for equivalent specs | — |
| Setup timeHonest first-install estimate, not the marketing quickstart. | 1 hour to run, a day to configure properly | — |
| Ongoing maintenanceThe part nobody budgets for. | Real and non-negotiable: backups you have actually restored, major-version upgrades roughly annually, and index maintenance as the data grows. | — |
PostgreSQL is Macrostack's recommended MongoDB Atlas alternative, so it's our pick here.
Weighing both against staying on MongoDB Atlas? Is MongoDB Atlas free? What it actually costs →
PostgreSQL
Strengths
- +JSONB covers most document workloads without giving up relational features
- +pgvector and full-text search built in — no second database
- +Governance by a foundation; the licence will not be changed under you
- +Every cloud offers a managed version, so you are never captive to one
Trade-offs
- −Migrating from MongoDB means rewriting queries, not just moving data
- −Horizontal sharding is harder than MongoDB's
- −Genuinely document-shaped workloads at huge scale fit MongoDB better
- −Operating it yourself is still real work
FerretDB
Strengths
- +Existing MongoDB drivers and queries keep working — minimal code change
- +Apache-2.0, with data resting in Postgres
- +Sidesteps the SSPL question entirely
- +Lets you consolidate onto one database engine
Trade-offs
- −Compatibility is good but not complete — test your aggregations
- −Extra layer between application and storage
- −Younger project with a smaller community
- −Not faster than MongoDB; this is about licence and consolidation
Which one fits you
The trade-offs above, turned into a decision. Find the line that describes your team.
Choose PostgreSQL
if a lower exit cost matters more to you than any single feature, and jSONB covers most document workloads without giving up relational features.
Choose FerretDB
if existing MongoDB drivers and queries keep working — minimal code change.
Neither, yet
if both carry a real cost you should weigh first — migrating from MongoDB means rewriting queries, not just moving data, and compatibility is good but not complete — test your aggregations. If either of those is a dealbreaker for your team, the shortlist is wrong rather than the choice.
What it takes to run these yourself
Real requirements and honest running costs, not the vendor quickstart.
PostgreSQL vs FerretDB — common questions
Is PostgreSQL a better fit than FerretDB for managed databases?
It depends on what you are optimising for, and the honest split is this: PostgreSQL scores 98 to FerretDB's 95 on data ownership and exit cost, so it is the safer choice if you care about being able to leave. FerretDB earns its place on a different axis — existing MongoDB drivers and queries keep working — minimal code change. Neither is a wrong answer for every team; the table above is the actual comparison.
What happens if we want to switch later?
PostgreSQL keeps its data local or in open formats, so leaving is an export rather than a negotiation. FerretDB is still self-hostable, so the files stay on your server either way — but it is not local-first by design, so check what its export produces before you rely on it.
Can I self-host PostgreSQL or FerretDB?
Both can be self-hosted. The difference is what it costs you in time rather than whether it is possible — see the setup and maintenance rows above.
Are PostgreSQL and FerretDB both alternatives to MongoDB Atlas?
Yes — both appear in our MongoDB Atlas comparison, which is why they are worth putting side by side. People usually arrive here already having decided to move off MongoDB Atlas and now choosing between the two replacements, which is a narrower and much easier question.
More MongoDB Atlas head-to-heads
Related alternative guides
Facts verified 2026-08-07. Licenses and pricing change — spotted something out of date? That's a correction we want.