PostgreSQL vs MongoDB: how to choose a database for a product
Clients ask “PostgreSQL vs MongoDB” because they want a safe choice for MVP that won’t explode later.
Here’s the short version: PostgreSQL is the safest default for most business products. MongoDB can be great, but only when it matches your data model and query patterns.
What you’re really choosing
- PostgreSQL: relational model, strong transactions, great reporting, mature tooling.
- MongoDB: document model, flexible schema, good for certain “document-like” workloads.
The key question is: What queries will you run every day?
Decision table
| If you need… | Pick | Why |
|---|---|---|
| Payments, subscriptions, orders, invoices | PostgreSQL | transactions + consistency |
| Reporting, dashboards, analytics-like queries | PostgreSQL | SQL is powerful |
| Complex relations (users ↔ roles ↔ items ↔ permissions) | PostgreSQL | relational model fits |
| Flexible documents with evolving structure | MongoDB | schema flexibility |
| High write throughput for event-like documents | MongoDB (sometimes) | depends on access patterns |
MVP rule of thumb (practical)
If you’re unsure, start with PostgreSQL. You can still:
- store JSON fields when flexibility is needed
- add Redis for caching
- add a specialized store later for specific workloads
The risk of “wrong Postgres” is usually lower than “wrong MongoDB for relational data”.
“Is MongoDB faster?”
Not automatically. Performance depends on:
- indexes
- query patterns
- document size
- operational setup
Bad schema design hurts both.
FAQ
Can we start with Postgres and add Mongo later?
Yes. Many systems are polyglot over time.
Do we need Redis?
Only if you have a clear caching/realtime need. Don’t add it “because everyone does”.
What about cost?
Operational simplicity usually favors Postgres for MVPs.
If you want, we can review your data model and queries and choose PostgreSQL vs MongoDB to avoid an expensive migration later.