PostgreSQL vs MongoDB
The core difference is the data model: PostgreSQL is a relational SQL database optimized for structured data and strong consistency, while MongoDB is a document database optimized for flexible schemas and native horizontal sharding.
At a glance
| Attribute | PostgreSQL | MongoDB |
|---|---|---|
| Data model | Relational (SQL) | Document (BSON) |
| Json support | Native JSONB | Native (document model) |
| Horizontal scaling | Via extensions/replicas Read replicas, partitioning, Citus for sharding | Native sharding |
| Acid | true Full ACID transactions | true Multi-document ACID since v4.0 |
| License | PostgreSQL License (permissive open source) | SSPL (source-available) Not OSI-approved open source since 2018 |
| First release | 1996 | 2009 |
Verdict: Choose PostgreSQL for relational, transaction-heavy data and a permissive open-source license; choose MongoDB when documents map naturally to your data and you want built-in horizontal scaling, accepting its source-available license.
Pros and cons
PostgreSQL
- Permissive open-source license
- Strong SQL compliance and rich data types
- Native JSONB for semi-structured data when needed
- Horizontal sharding requires extensions or external tooling
MongoDB
- Flexible document schema
- Native sharding for horizontal scale
- Natural fit for JSON-shaped data
- SSPL license is source-available, not OSI open source
- Relational joins are less natural than in SQL
Overview
PostgreSQL and MongoDB solve overlapping problems from opposite starting points. PostgreSQL is relational-first with optional JSON; MongoDB is document-first with optional relational-style modeling.
Choosing between them
Pick PostgreSQL when your data is naturally relational, you need complex queries and joins, or you require a permissive open-source license. Pick MongoDB when your data is naturally document-shaped and you want built-in horizontal sharding without external tooling.
Frequently asked questions
- Is PostgreSQL or MongoDB better for transactions?
- Both support ACID transactions, but PostgreSQL has a longer track record with complex multi-table transactional workloads, while MongoDB added multi-document ACID transactions in version 4.0.
- Can PostgreSQL store JSON like MongoDB?
- Yes. PostgreSQL's native JSONB type stores and indexes JSON documents, so you can mix relational and document-style data in one database.