I'm building a SaaS app, should I use PostgreSQL as the main database?

Yes — PostgreSQL is usually the best default choice for a SaaS app’s main database.

Why PostgreSQL is a strong default

• Reliable and mature: very battle-tested for production SaaS.
• Great for multi-tenant apps: easy to model tenant isolation with shared tables, separate schemas, or separate databases.
• Strong consistency and transactions: important for billing, permissions, workflows, and audit logs.
• Flexible data modeling: relational data by default, plus JSONB when you need semi-structured data.
• Powerful querying: indexes, full-text search, window functions, CTEs, etc.
• Good ecosystem: widely supported by ORMs, cloud providers, BI tools, backups, migrations, and observability platforms.
• Scales well enough for most SaaS: with proper indexing, caching, read replicas, and partitioning when needed.

When PostgreSQL is especially a good fit

Use it if your SaaS has:

• users, orgs, teams, permissions
• subscriptions, invoices, usage tracking
• audit logs
• reporting/dashboard queries
• transactional workflows
• moderate to high data integrity requirements

When you might choose something else

Consider alternatives if:

• your data is mostly massive write throughput with simple access patterns and you don’t need relational queries
• you need global low-latency writes across many regions from day one
• your workload is mostly event streaming / analytics rather than transactional app data
• you already know a specific managed service fits better for your team and constraints

Practical recommendation

For most SaaS startups:

• Use PostgreSQL as the primary database
• add Redis for caching/queues/session data if needed
• consider a separate analytics store later if reporting becomes heavy

If you want, I can also recommend:

1. a Postgres schema strategy for multi-tenancy, or
2. the best DB stack for your specific SaaS based on your product and scale.