Nestjs Foundation

NestJS Foundation

Purpose

Define the foundation of an approved NestJS API: module boundaries per domain, DI/provider conventions, the request lifecycle (pipes → guards → interceptors → filters), and configuration — so the framework's structure serves the domains rather than ceremony.

When to Use

• After backend-stack-selection chose NestJS and Gate 2 approved it.
• Not for Express (express-foundation) or before the stack decision.

Inputs

• Approved stack decision and architecture (../../architecture-design).
• Domain list, team conventions, async/realtime needs (queues, WebSockets, schedules).

Discovery Questions

• What are the domains, and which share providers?
• Which cross-cutting concerns are global (validation pipe, auth guard, exception filter)?
• Are queues/WebSockets/scheduling in scope now (Nest modules for each)?

Responsibilities

• Define modules per domain, each owning its controllers, services, and data providers; shared code in explicit shared modules — no circular imports.
• Set the request lifecycle: global ValidationPipe (whitelist, transform), guards for authn/authz, interceptors for logging/serialization, exception filters mapping to the error contract (backend-error-handling).
• Plan ConfigModule with validated env schema (fail fast).
• Note where Nest's ecosystem covers approved needs (queues, WebSocket gateways, schedule module) — each still a justified choice.
• Keep providers injectable and testable; no service locators or hidden singletons.

Required Workflow

1. Confirm approval + architecture inputs.
2. Map domains → modules; mark shared modules explicitly.
3. Define global pipes/guards/interceptors/filters and their order.
4. Define config + env validation.
5. Record the foundation plan; implementation follows approved tasks only.

Decision Rules

• One module per domain; split only when a module grows multiple concerns.
• Global validation pipe with whitelist: true — unknown fields never reach services.
• Authorization is a guard + service-level check, not controller ifs (backend-authorization).
• Prefer Nest-native integrations for queues/WebSockets/scheduling when those needs are approved — coherence is why NestJS was chosen.

Rules

• No scaffolding or dependency installation before task approval (Gate 4).
• Module boundaries mirror the architecture's domain boundaries.
• Every global concern (pipe/guard/filter) recorded — they are invisible in handlers.

Anti-Patterns

• One giant AppModule with everything registered globally.
• Circular module imports patched with forwardRef instead of fixing boundaries.
• Business logic in controllers or guards.
• Adopting every Nest feature (CQRS, microservices) without a requirement.

Validation Checklist

• Domain → module map defined; shared modules explicit; no cycles.
• Global pipes/guards/interceptors/filters planned and ordered.
• Config module + env validation planned (fail fast).
• Async/realtime module needs noted against approvals.
• Nothing installed or scaffolded yet.

Definition of Done

A recorded NestJS foundation plan — module map, request lifecycle, config, conventions — ready to drive approved implementation tasks for a multi-developer codebase.

Related Skills

backend-stack-selection, backend-api-architecture, backend-validation, backend-error-handling, backend-authorization, queues, realtime-communication, scheduled-jobs.

Related Knowledge

../../../knowledge/ (domain boundaries, team conventions).

Related References

../../../references/backend/nestjs/ (module examples, when populated).

Context Loading Guidance

• Requires: approved stack decision, domain list, architecture summary.
• Does not require: database internals, other packs, unrelated references.
• May load: backend-api-architecture, backend-authorization (guard design).
• Stop when: the foundation plan is recorded.

Token Efficiency Guidance

Plan at module-map altitude; a domain→module table beats generated code. Delegate lifecycle details to the specialist skills.