# Willyu1007 AI First Template Backend Dev Guidelines > Backend Development Guidelines (Node.js / Express / TypeScript) - Skill: `tomevault-io/willyu1007-ai-first-template-backend-dev-guidelines` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/willyu1007-ai-first-template-backend-dev-guidelines` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/willyu1007-ai-first-template-backend-dev-guidelines/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/willyu1007-ai-first-template-backend-dev-guidelines --- # Backend Development Guidelines (Node.js / Express / TypeScript) This skill collects reusable backend patterns for services built with Node.js, Express, and TypeScript. --- ## Purpose - Establish a consistent structure for backend services. - Reduce bugs by separating concerns (routing vs business logic vs data access). - Make failures observable (error tracking + structured logs). - Make changes testable (clear boundaries, predictable inputs/outputs). --- ## When to Use Use this skill when working on: - Routes / controllers / request handlers - Service-layer business logic - Repository/data-access patterns (e.g., Prisma) - Middleware (auth, validation, error boundaries) - Configuration management - Monitoring/error tracking and performance spans - Testing and refactoring backend code --- ## Quick Start ### New endpoint checklist - [ ] **Route**: defines HTTP method + path + middleware only - [ ] **Controller**: parses input, validates, calls service, formats response - [ ] **Service**: implements business logic; no HTTP knowledge - [ ] **Repository**: encapsulates DB access and query construction (when non-trivial) - [ ] **Validation**: schema-validated inputs (e.g., Zod) - [ ] **Monitoring**: capture exceptions and add key spans - [ ] **Tests**: unit tests for service/repo; integration tests for route ### New service checklist - [ ] `src/config/` centralized config loading/validation - [ ] `src/middleware/` includes auth + request context + error boundary - [ ] `src/routes/` delegates to controllers - [ ] `src/controllers/` follows a consistent error-handling pattern - [ ] Monitoring is initialized early in process startup --- ## Core principles (high signal) 1. **Routes only route** (no business logic in routes) 2. **Controllers handle HTTP, services handle business rules** 3. **Validate all external inputs** (params/body/query) 4. **Centralize configuration** (avoid scattered `process.env` access in app code) 5. **Capture and contextualize errors** (monitoring + structured logs) 6. **Repositories for complex DB access** (avoid scattered queries) 7. **Test at the right layer** (fast unit tests + targeted integration tests) --- ## Related Skills | Need to… | Skill | |---------|------| | Understand layered architecture | `architecture-overview` | | Build routes + controllers | `routing-and-controllers` | | Structure services + repositories | `services-and-repositories` | | Validate inputs | `validation-patterns` | | Add monitoring / error tracking | `sentry-and-monitoring` | | Create middleware | `middleware-guide` | | Database access patterns | `database-patterns` | | Configuration patterns | `configuration` | | Async + error patterns | `async-and-errors` | | Testing strategy | `testing-guide` | | End-to-end examples | `complete-examples` | --- > Source: [willyu1007/AI_First_Template](https://github.com/willyu1007/AI_First_Template) — distributed by [TomeVault](https://tomevault.io).