MongoDB vs PostgreSQL
MongoDB is a document database that most buyers meet as the Atlas cloud service, and a paid ladder that begins at a free cluster. PostgreSQL is a relational engine from a community project that sells nothing, so the money goes to whichever host or support firm you choose. The licences differ too: MongoDB's server is under its own SSPL, while PostgreSQL uses a permissive licence the project says it will not change.
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Choose MongoDB ifyou build around JSON documents, want a managed cloud service with a published hourly price, and can live with a server licence that is not OSI approved.
Choose PostgreSQL ifyou want a relational engine that no company can reprice, and you are willing to pick a host or support firm yourself.
MongoDB and PostgreSQL side by side
| MongoDB | PostgreSQL | |
|---|---|---|
| Our database management system rank | #5 of 19 | #1 of 19 |
| Established in | United States | Not stated by the vendor |
| List price, 2 November 2026 | Atlas: Free tier 512 MB, then Flex (5 GB, up to $30 monthly), then Dedicated (10 GB through 4 TB, from $56.94 monthly). All hourly metered | Hosting and support bought separately from third parties; the engine itself is free (PostgreSQL License) |
| Free tier | Yes | Yes |
| Open source | — | Yes |
| Self-hostable | — | — |
| Built for | Teams building around JSON documents who prefer a managed cloud service | Teams that want a relational engine with no vendor able to reprice it |
| Not for | Buyers who need an OSI-approved licence for the server | Buyers wanting one company accountable for support and uptime |
Both are reviewed in full in our database management system ranking: MongoDB and PostgreSQL.
Where they differ
MongoDB 1 · PostgreSQL 3 · open 1- 01
What you pay to start
The MongoDB pricing page shows three Atlas steps: a 512 MB Free cluster, 5 GB Flex that costs up to $30 per month, and an hourly-billed Dedicated tier covering 10 GB to 4 TB with a $56.94 monthly starting price. PostgreSQL has no plan to buy: the engine is free, and hosting comes from third parties listed on the project site. MongoDB gives a clearer first bill, PostgreSQL a lower floor.
Edge: PostgreSQL
- 02
Licence terms
PostgreSQL ships under its own PostgreSQL License, which the project likens to BSD or MIT, and it says a change is not planned. MongoDB's server code has been under the SSPL v1 since 16 October 2018, and section 13 requires the service source code to be released if you offer the program to third parties as a service.
Edge: PostgreSQL
- 03
Who is accountable when it breaks
With MongoDB there is one company to call, and Enterprise Advanced adds a commercial licence for self-managed use, though its price is given only through sales. PostgreSQL has no single vendor: the project lists commercial support companies run by third parties and sells no plan itself.
Edge: MongoDB
- 04
Cost growth as features are added
MongoDB lists Search, Vector Search, Stream Processing and Data Federation on separate pricing pages, so each feature you adopt adds a line to the bill. PostgreSQL describes itself as extensible, with no per-feature meter in the licence.
Edge: PostgreSQL
- 05
Upgrades and leaving
PostgreSQL supports each major version for 5 years, and moving to a new major version means dump/reload or pg_upgrade. Its pg_dump exports a database consistently without blocking readers or writers. We found no export or upgrade facts for MongoDB in the vendor pages we checked, so this round is not scored in either direction.
Depends on the buyer
When neither fits
If you need a key-value cache rather than a primary store, or a masterless engine built for heavy write loads, look at Redis or Apache Cassandra instead.
MongoDB or PostgreSQL: questions
3 answersIs MongoDB open source?
MongoDB's server is published under the Server Side Public License v1, which MongoDB, Inc. wrote itself.
Its own licence page describes a duty to publish the service's source code if the program is run as a service for third parties. PostgreSQL uses the PostgreSQL License, a permissive licence.
Which is cheaper to start with?
Both can start at no cost: MongoDB with a 512 MB Atlas Free cluster, PostgreSQL as free software. After that, MongoDB's Flex step stops at $30 per month, while PostgreSQL costs whatever your chosen host or support company charges.
Where are the two vendors based?
MongoDB's terms of use give legal address 1633 Broadway, New York, USA. PostgreSQL is a community project, and the project does not state a country of establishment.
Sources
Checked 2 November 2026- MongoDB pricing page: Atlas Free, Flex, Dedicated; Search and similar services priced apart; Enterprise Advanced sold by sales.
- MongoDB Server Side Public License: section 13 duty, authored by MongoDB.
- MongoDB server repository: server code under SSPL v1 from 16 October 2018.
- MongoDB terms of use: New York legal address.
- PostgreSQL licence page: licence likened to BSD or MIT, no change planned.
- PostgreSQL versioning policy: support window of 5 years, how majors are upgraded.
- PostgreSQL professional support: third-party support and hosting lists, no sold plan, no country stated.
- pg_dump documentation: export stays consistent, readers and writers not blocked.