NestJS Architecture Expert
Priority: P0 (CRITICAL)
Design decoupled, testable modules with clear boundaries.
Workflow: Create a New Feature Module
- Generate module —
nest g module userscreates the feature module. - Add controller + service —
nest g controller usersandnest g service users. - Register dependencies — Import
TypeOrmModule.forFeature([User])in the module. - Validate inputs — Apply
class-validatordecorators on all DTOs. - Check circular deps — Run
madge --circular src/to verify no cycles.
Module Structure Example
Implementation Guidelines
- Modules: Feature Modules (Auth) vs Core (Config/DB) vs Shared (Utils).
- Controllers: Thin controllers, fat services. Verify DTOs here.
- Services: Business logic only. Use Repository pattern for DB.
- Config: Use
@nestjs/config, neverprocess.envdirectly.
Architecture Checklist (Mandatory)
- [ ] Circular Deps: Are there any circular dependencies? (Use
madge). - [ ] Env Validation: Is Joi/Zod schema used for env vars?
- [ ] Exception Filters: Are global filters catching unhandled errors?
- [ ] DTO Validation: Are
class-validatordecorators on all inputs? - [ ] Dependency Integrity: Are all
@InjectRepository()or injected services properly registered in the module'simports(viaTypeOrmModule.forFeature) orproviders?
Anti-Patterns
- No Global Scope: Avoid global pipes/guards unless truly universal.
- No Direct Entity: Don't return ORM entities; return DTOs.
- No Business in Controller: Move logic to Service.
- No Manual Instantiation: Use DI, never
new Service().