What are provider scopes in NestJS and when would you change the default?

Q: What are provider scopes in NestJS and when would you change the default?

@Injectable({ scope: Scope.REQUEST }) export class RequestScopedService { constructor(@Inject(REQUEST) private request: Request) {} } DEFAULT (singleton) — one shared instance for the app lifetime. Best for stateless services. REQUEST — new instance per request. Use when service needs request context (e.g., tenant ID, user from JWT). TRANSIENT — new instance per injection point. Rarely needed; for stateful utilities. Warning: REQUEST scope propagates — every consumer of a request-scoped provider also becomes request-scoped, impacting performance.

Difficulty: 6/10

provider scope types, singleton vs request scope, dependency injection lifecycle

Provider scope controls instance lifetime. DEFAULT (singleton) creates one instance for the whole app. REQUEST creates a new instance per incoming request — useful for tenant/user context. TRANSIENT creates a new instance per injection point. Request scope propagates up the dependency chain, which can hurt performance.

Setting provider scope

The three scopes:

1
DEFAULT (singleton) — one shared instance for the app lifetime. Best for stateless services.
2
REQUEST — new instance per request. Use when service needs request context (e.g., tenant ID, user from JWT).
3
TRANSIENT — new instance per injection point. Rarely needed; for stateful utilities.
4
Warning: REQUEST scope propagates — every consumer of a request-scoped provider also becomes request-scoped, impacting performance.

Scenario Questions

0-2 years experience

2-5 years experience

Follow-up Questions