# Backend Nestjs

> NestJS backend development patterns. Use when developing backend APIs with NestJS, TypeORM/Prisma, and TypeScript. Use when this capability is needed.

- Skill: `tomevault-io/backend-nestjs` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/backend-nestjs`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/backend-nestjs/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/backend-nestjs

---


# NestJS Backend Development

## When to Use This Skill

Use when developing backend code in a NestJS project with TypeScript.

## Recommended Project Structure

```
src/
├── core/
│   ├── config/              # Configuration (env validation)
│   ├── database/            # Database connections, migrations
│   ├── guards/              # Auth guards
│   ├── interceptors/        # Request/response interceptors
│   ├── filters/             # Exception filters
│   └── decorators/          # Custom decorators
├── modules/
│   └── <domain>/
│       ├── application/     # Use cases / services
│       ├── domain/          # Entities, value objects, interfaces
│       ├── infrastructure/  # Repositories, external services
│       ├── presentation/    # Controllers, DTOs, validators
│       └── <domain>.module.ts
├── shared/
│   ├── utils/
│   ├── types/
│   └── constants/
└── main.ts
```

## Conventions

- One use case per file in `application/`
- DTOs with class-validator decorators in `presentation/`
- Repository pattern for data access in `infrastructure/`
- Module-scoped providers; export only what's needed

## Testing

- Stack: Vitest (preferred) or Jest
- Unit test use cases with mocked dependencies
- Test file next to source: `*.spec.ts`
- All tests in English
- Naming: "should do X when Y"

## Commands

```bash
pnpm dev          # Development with hot reload
pnpm build        # Production build
pnpm lint         # ESLint
pnpm test         # Run tests
pnpm test:cov     # Coverage report
```

## Error Handling

- Use NestJS built-in exceptions (BadRequestException, NotFoundException, etc.)
- Custom exceptions extend HttpException
- Global exception filter for unhandled errors

## Database

- Use query builder or repository pattern
- Always use transactions for multi-table writes
- Add indexes for frequently queried columns
- Use database MCPs to inspect schema before writing queries

## Pre-commit Checklist

- Build passes? (`pnpm build`)
- Lint passes? (`pnpm lint`)
- Tests pass? (`pnpm test`)
- DTOs have proper validation?
- Error cases handled?

---
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<!-- tomevault:4.0:skill_md:2026-04-11 -->