| name | nestjs-database |
| description | Data access patterns, Scaling, Migrations, and ORM selection. Use when implementing TypeORM/Prisma repositories, migrations, or database patterns in NestJS. (triggers: **/*.entity.ts, prisma/schema.prisma, TypeOrmModule, PrismaService, MongooseModule, Repository) |
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.
- Generation: Whenever a TypeORM entity (
.entity.ts) is modified, a migration MUST be generated using pnpm migration:generate.
- Audit: Always inspect the generated migration file to ensure it matches the entity changes before applying.
- Production Strategies:
- CI/CD Integration (Recommended): Run
pnpm migration:run in a pre-deploy or post-deploy job (e.g., GitHub Actions, GitLab CI). Ensure the production environment variables are correctly set.
- Manual SQL (For restricted DB access): Use
typeorm migration:show to get the SQL or simply copy the up method's SQL into a management tool (like Supabase SQL Editor). Always track manual runs in the migrations metadata table.
- Zero-Downtime: Use Expand-Contract pattern (Add -> Backfill -> Drop) for destructive changes.
- Seeding: Use factories for dev data; only static dicts for prod.
Best Practices
- Pagination: Mandatory. Use limit/offset or cursor-based pagination.
- Indexing: Define indexes in code (decorators/schema) for frequently filtered columns (
where, order by).
- Transactions: Use
QueryRunner (TypeORM) or $transaction (Prisma) for all multi-step mutations to ensure atomicity.
Anti-Patterns
- No synchronize in production: Use explicit migrations;
synchronize: true drops and recreates columns.
- No raw entity returns from services: Map to DTOs before leaving the service layer.
- No unpaginated list queries: All list endpoints must implement limit/offset or cursor pagination.
