Comparison
PostgreSQL vs MongoDB
A relational database against a document database. Not about "SQL vs NoSQL", but about the shape of your data.
| Aspect | PostgreSQL | MongoDB |
|---|---|---|
| Data model | Tables with a schema, relations, JSONB for flexible fields | Collections of JSON-like documents (BSON), flexible schema |
| Relations and joins | Core strength, foreign keys, multi-table joins | $lookup exists, but embedding data in the document is the natural way |
| Transactions | Full ACID for any query | Multi-document ACID since 4.0, but costlier than single-document operations |
| Horizontal scaling | Read replicas, sharding via Citus or by hand | Built-in sharding and replica sets |
| Schema changes | Migrations, discipline, but integrity guarantees | Fast changes, but data consistency falls on the application |
| License | PostgreSQL License | SSPL (not OSI open source) |
| Maintainer | Independent PostgreSQL community | MongoDB, Inc., with the managed Atlas service |
| Best for | Most business apps, reporting, consistent data | Catalogs with varied attributes, event and content data |
Choose PostgreSQL when
- The data has clear relations: users, orders, payments.
- You need complex queries and reporting.
- You are unsure about future data shape: PostgreSQL with JSONB covers both worlds.
Choose MongoDB when
- A document is naturally read and written whole, with few relations.
- Records differ a lot in structure.
- You need built-in horizontal scaling from day one.
Bottom line
Default to PostgreSQL: with JSONB it covers most "document" needs. MongoDB is justified when the data really is document-shaped and sharded scaling is planned up front.
Compared
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