fastify-best-practices

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](rules/plugins.md) - Plugin development and encapsulation
• [rules/routes.md](rules/routes.md) - Route organization and handlers
• [rules/schemas.md](rules/schemas.md) - JSON Schema validation
• [rules/error-handling.md](rules/error-handling.md) - Error handling patterns
• [rules/hooks.md](rules/hooks.md) - Hooks and request lifecycle
• [rules/authentication.md](rules/authentication.md) - Authentication and authorization
• [rules/testing.md](rules/testing.md) - Testing with inject()
• [rules/performance.md](rules/performance.md) - Performance optimization
• [rules/logging.md](rules/logging.md) - Logging with Pino
• [rules/typescript.md](rules/typescript.md) - TypeScript integration
• [rules/decorators.md](rules/decorators.md) - Decorators and extensions
• [rules/content-type.md](rules/content-type.md) - Content type parsing
• [rules/serialization.md](rules/serialization.md) - Response serialization
• [rules/cors-security.md](rules/cors-security.md) - CORS and security headers
• [rules/websockets.md](rules/websockets.md) - WebSocket support
• [rules/database.md](rules/database.md) - Database integration patterns
• [rules/configuration.md](rules/configuration.md) - Application configuration
• [rules/deployment.md](rules/deployment.md) - Production deployment
• [rules/http-proxy.md](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