PostgreSQL vs MongoDB for SaaS should follow your data shape. Most subscription products are relational (accounts, plans, entitlements); document stores shine for flexible content and event-like payloads.
PostgreSQL advantages for SaaS
- Strong transactions for billing and seats
- Mature joins for reporting
- Row-level security patterns for tenancy
- Rich indexing and operational tooling
MongoDB advantages
- Flexible documents when schema evolves weekly
- Horizontal scaling patterns for certain workloads
- Natural fit for content/catalog blobs
- Good when access patterns are document-centric
Default recommendation
Start with PostgreSQL for multi-tenant SaaS unless you have a clear document-first domain. You can still store JSON in Postgres. See multi-tenant architecture and SaaS stack guide.
Ops considerations
- Backups, PITR and restore drills
- Connection pooling at scale
- Migration discipline
- Observability on slow queries
Mixed architectures
Postgres as system of record + Mongo/search for specific features is common. Keep a single source of truth for money and permissions. Delivered via SaaS development and cloud.
Validate with your schema sketch
Contact us with entity diagrams and we will recommend primary + secondary stores.