When to use

Use this skill when you need to:

• Develop backend applications using Fastify

• Implement Fastify plugins and route handlers

• Get guidance on Fastify architecture and patterns

• Use TypeScript with Fastify (strip types)

• Implement testing with Fastify's inject method

• Configure validation, serialization, and error handling

Quick Start

A minimal, runnable Fastify server to get started immediately:

import Fastify from 'fastify'

const app = Fastify({ logger: true })

app.get('/health', async (request, reply) => { return { status: 'ok' } })

const start = async () => { await app.listen({ port: 3000, host: '0.0.0.0' }) } start()

Recommended Reading Order for Common Scenarios

• New to Fastify? Start with plugins.md → routes.md → schemas.md

• Adding authentication: plugins.md → hooks.md → authentication.md

• Improving performance: schemas.md → serialization.md → performance.md

• Setting up testing: routes.md → testing.md

• Going to production: logging.md → configuration.md → deployment.md

How to use

Read individual rule files for detailed explanations and code examples:

• rules/plugins.md - Plugin development and encapsulation

• rules/routes.md - Route organization and handlers

• rules/schemas.md - JSON Schema validation

• rules/error-handling.md - Error handling patterns

• rules/hooks.md - Hooks and request lifecycle

• rules/authentication.md - Authentication and authorization

• rules/testing.md - Testing with inject()

• rules/performance.md - Performance optimization

• rules/logging.md - Logging with Pino

• rules/typescript.md - TypeScript integration

• rules/decorators.md - Decorators and extensions

• rules/content-type.md - Content type parsing

• rules/serialization.md - Response serialization

• rules/cors-security.md - CORS and security headers

• rules/websockets.md - WebSocket support

• rules/database.md - Database integration patterns

• rules/configuration.md - Application configuration

• rules/deployment.md - Production deployment

• rules/http-proxy.md - HTTP proxying and reply.from()

Core Principles

• Encapsulation: Fastify's plugin system provides automatic encapsulation

• Schema-first: Define schemas for validation and serialization

• Performance: Fastify is optimized for speed; use its features correctly

• Async/await: All handlers and hooks support async functions

• Minimal dependencies: Prefer Fastify's built-in features and official plugins