When should your business use PostgreSQL (Supabase) versus a document database like Firestore?
Direct Answer: Use PostgreSQL (such as Supabase) when your business relies on relational data, complex analytical joins, strict financial auditing, and predictable flat-rate cloud hosting. Choose a document store like Firestore only when your primary requirement is offline-first mobile synchronization with simple document lookups. For data-heavy dashboards and SaaS products, Firestore’s pay-per-read billing quickly becomes cost-prohibitive.
Predictable Long-Term Cost
A single reporting dashboard in Firestore can trigger tens of thousands of read charges in a single executive session. PostgreSQL instances offer predictable compute costs regardless of read volume, combined with ACID guarantees that ensure calculations never go out of balance.
| Architectural Dimension | Firestore (NoSQL Document Store) | PostgreSQL / Supabase (Relational) |
|---|---|---|
| Complex Queries & Joins | No native joins; requires client-side merging and duplicate data writes | Native SQL joins, aggregations, CTEs, and window functions |
| Pricing Model at Scale | Pay-per-operation; read spikes multiply operational bills instantly | Flat compute instance pricing; unlimited query reads and writes |
| Multi-Tenant Isolation | Application-layer security rules; easy to misconfigure in complex models | Engine-level Row-Level Security (RLS); mathematically isolates tenant accounts |
| Data Integrity Enforcement | Schema-less; structural mistakes propagate silently across documents | Strict foreign keys, unique constraints, and check validations at write time |