ReddRadar
Agent skill
fastify
Provides comprehensive guidance for Fastify framework including routing, plugins, JSON schema validation, hooks, serialization, and performance optimization. Use when the user asks about Fastify, needs to create high-performance Node.js applications, implement plugins, or optimize API performance.
Install this agent skill to your Project
npx add-skill https://github.com/partme-ai/full-stack-skills/tree/main/skills/nodejs-skills/fastify
SKILL.md
When to use this skill
Use this skill whenever the user wants to:
- Build high-performance Node.js HTTP services with Fastify
- Use JSON Schema for request/response validation and serialization
- Create and compose Fastify plugins with encapsulation
- Configure logging, TypeScript, and production deployments
How to use this skill
Workflow
- Create server — instantiate Fastify with options (logging, etc.)
- Register plugins — add functionality via the plugin system
- Define routes with schemas — validate requests and serialize responses
- Test and deploy — use
fastify.inject()for testing, deploy with process manager
Quick Start Example
const fastify = require('fastify')({ logger: true });
// Register plugins
fastify.register(require('@fastify/cors'));
fastify.register(require('@fastify/helmet'));
// Route with JSON Schema validation
fastify.post('/api/items', {
schema: {
body: {
type: 'object',
required: ['name', 'price'],
properties: {
name: { type: 'string', minLength: 1 },
price: { type: 'number', minimum: 0 },
},
},
response: {
201: {
type: 'object',
properties: {
id: { type: 'integer' },
name: { type: 'string' },
price: { type: 'number' },
},
},
},
},
handler: async (request, reply) => {
const item = await createItem(request.body);
reply.code(201).send(item);
},
});
fastify.get('/api/items/:id', async (request, reply) => {
const item = await getItem(request.params.id);
if (!item) {
reply.code(404).send({ error: 'Not found' });
return;
}
return item;
});
fastify.listen({ port: 3000, host: '0.0.0.0' });
Plugin Pattern
// plugins/db.js
async function dbPlugin(fastify, options) {
const pool = createPool(options.connectionString);
fastify.decorate('db', pool);
fastify.addHook('onClose', async () => pool.end());
}
module.exports = require('fastify-plugin')(dbPlugin);
// app.js
fastify.register(require('./plugins/db'), {
connectionString: process.env.DATABASE_URL,
});
Error Handling
fastify.setErrorHandler((error, request, reply) => {
request.log.error(error);
const statusCode = error.statusCode || 500;
reply.code(statusCode).send({
error: error.message,
statusCode,
});
});
Best Practices
- Define JSON Schema for all request bodies and responses — enables fast serialization
- Use
fastify-pluginto break encapsulation when sharing decorators across scopes - Leverage built-in Pino logger; avoid
console.login production - Use hooks (
onRequest,preHandler) for cross-cutting concerns - Test routes with
fastify.inject()without starting a server
Reference
- Official documentation: https://fastify.dev/docs/latest/
Keywords
fastify, Node.js, high performance, JSON schema, plugins, serialization, hooks, Pino logger
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