nestjs-best-practices

Circular dependencies are resolved by extracting shared logic into a third module that both modules import, or by using event-driven communication with @nestjs/event-emitter so modules react to events without direct imports. Forward references work but indicate architectural problems.

Organize code into self-contained feature modules where each domain (users, orders) holds its own controllers, services, entities, and DTOs. Avoid grouping by technical layer, and export only the providers other modules actually need.

Use class-validator decorators on DTO classes combined with a global ValidationPipe configured with whitelist and transform options. Built-in pipes like ParseUUIDPipe and ParseIntPipe handle common parameter transformations declaratively.

Yes, use the relations option in find calls or QueryBuilder joins to eager-load related entities in a single query. For GraphQL, DataLoader batches per-request queries, and enabling query logging in development helps detect N+1 patterns.

Reserve @Global() for truly cross-cutting concerns like configuration, logging, and database connections. Overusing it hides dependencies, complicates testing, and makes module requirements invisible from import declarations.

The synchronize option can drop columns, tables, or data when entity schemas change, making it unsafe for production. Use TypeORM migrations instead, which provide versioned, reversible schema changes consistent across all environments.