What do most startups use for their primary database, PostgreSQL or something else?

For most startups, PostgreSQL is the default primary database.

Why Postgres is so common

• Reliable and mature: battle-tested, widely trusted
• Flexible: handles structured data well and also supports JSON/JSONB
• Powerful enough for early and mid-stage products: good indexing, transactions, joins, constraints
• Low operational burden: easy to run on managed services like AWS RDS, Supabase, Neon, Heroku, etc.
• Large ecosystem: lots of tooling, ORM support, and developer familiarity

What else startups use

Depending on the product, some startups choose:

• MySQL: still common, especially if teams already know it or are using certain hosting/platform defaults
• MongoDB: for document-heavy apps, though less often as the main “default” than it used to be
• DynamoDB / Firestore / Supabase / etc.: when the app architecture strongly benefits from managed NoSQL or serverless patterns
• SQLite: often for prototypes, local-first apps, or very small deployments

Typical pattern

A lot of startups start with:

• Postgres as the main transactional database
• Redis for caching/queues/sessions
• Maybe a search engine or analytics store later

Bottom line

If you mean “what is the most common primary database choice for startups?”, the answer is PostgreSQL.

If you want, I can also give you:

1. a startup database decision guide, or
2. a Postgres vs MySQL vs MongoDB comparison for new products.