| # ADR-001: Use PostgreSQL instead of MongoDB | |
| ## Status | |
| Accepted | |
| ## Context | |
| We need a relational database to support complex joins and ACID transactions. We considered MongoDB for its flexible schema but it lacks transactional guarantees across documents. | |
| ## Decision | |
| We'll use PostgreSQL. | |
| ## Consequences | |
| - Gains: strong consistency, mature tooling, powerful query engine. | |
| - Costs: more up-front schema design, learning curve for some devs. | |