Every domain is a standalone NestJS Module

Domain logic trapped in AppModule — libs stay empty shells.

NestJS·NestJS Modules·Medium·Since 2026-05-01

nestjs-module-domain-standalone

Why it matters

Failure modes if this rule is ignored

Stake	If ignored
Can't run alone	Domain code lives only in AppModule — libs are empty and the domain can't load elsewhere.
Agent gets lost	Without this, all controllers and services live in the app and the libs are empty — and rule 1 (domain separation) becomes decoration.

How to fix

In Nx + NestJS, a domain becomes a Module that lives in libs/<domain>/backend-feature-* (or similar). The backend app only assembles those modules in AppModule.

Examples

Bad

// apps/api/src/app.module.ts
@Module({
  controllers: [SitesController, AgentsController, UsersController, BillingController],
  providers: [SitesService, AgentsService, UsersService, BillingService, PrismaService],
})
export class AppModule {}

Good

// libs/sites-management/backend-feature/src/lib/sites.module.ts
@Module({
  imports: [SitesDataAccessModule],
  controllers: [SitesController],
  providers: [SitesService],
  exports: [SitesService],          // ← only what's public
})
export class SitesModule {}

// libs/studio/backend-feature/src/lib/studio.module.ts
@Module({
  imports: [StudioDataAccessModule],
  controllers: [AgentsController],
  providers: [AgentsService],
  exports: [AgentsService],
})
export class StudioModule {}

// apps/api/src/app.module.ts
@Module({
  imports: [SitesModule, StudioModule, AccountModule],
})
export class AppModule {}

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