NestJS Database Standards

Priority: P0 (FOUNDATIONAL)

Database integration patterns and ORM standards for NestJS applications.

Selection Strategy

See references/persistence_strategy.md for database selection matrix and scaling patterns (Connection Pooling, Sharding).

Patterns

• Repository Pattern: Isolate database logic.
• TypeORM: Inject @InjectRepository(Entity).
• Prisma: Create a comprehensive PrismaService.
• Abstraction: Services should call Repositories, not raw SQL queries.

Configuration (TypeORM)

• Async Loading: Always use TypeOrmModule.forRootAsync to load secrets from ConfigService.
• Sync: Set synchronize: false in production; use migrations instead.

Migrations

• Never use synchronize: true in production.
• Execution: Run via init container or CD step.
• Zero-Downtime: Use Expand-Contract pattern (Add -> Backfill -> Drop).
• Seeding: Use factories for dev data; only static dicts for prod.

Best Practices

1. Pagination: Mandatory. Use limit/offset or cursor-based pagination.
2. Indexing: Define indexes in code (decorators/schema) for frequently filtered columns (where, order by).
3. Transactions: Use QueryRunner (TypeORM) or $transaction (Prisma) for all multi-step mutations to ensure atomicity.