---
name: fastify-4f0626e47cad
description: "Production Fastify (TypeScript) patterns: schema validation, plugins, typed routes, error handling, security hardening, logging, testing with inject, and graceful shutdown"
version: 1.0.0
category: toolchain
author: Claude MPM Team
license: MIT
progressive_disclosure:
  entry_point:
    summary: "Build fast, type-safe Node APIs with Fastify using schema-first validation, plugin encapsulation, and production middleware patterns"
    when_to_use: "When building TypeScript backends needing high performance, schema-based validation, clean plugin composition, and strong testability"
    quick_start: "1. Create Fastify instance 2. Add Type Provider (Zod/TypeBox) 3. Register plugins (CORS/Helmet) 4. Add error handler + logging 5. Test with inject()"
  token_estimate:
    entry: 130
    full: 5200
context_limit: 900
tags:
  - typescript
  - fastify
  - nodejs
  - api
  - validation
  - json-schema
  - security
  - testing
requires_tools: []
---

# Fastify (TypeScript) - Production Backend Framework

## Overview

Fastify is a high-performance Node.js web framework built around JSON schema validation, encapsulated plugins, and great developer ergonomics. In TypeScript, pair Fastify with a type provider (Zod or TypeBox) to keep runtime validation and static types aligned.

## Quick Start

### Minimal server

✅ **Correct: basic server with typed response**
```ts
import Fastify from "fastify";

const app = Fastify({ logger: true });

app.get("/health", async () => ({ status: "ok" as const }));

await app.listen({ host: "0.0.0.0", port: 3000 });
```

❌ **Wrong: start server without awaiting listen**
```ts
app.listen({ port: 3000 });
console.log("started"); // races startup and hides bind failures
```

## Schema Validation + Type Providers

Fastify validates requests/responses via JSON schema. Use a type provider to avoid duplicating types.

### Zod provider (recommended for full-stack TypeScript)

✅ **Correct: Zod schema drives validation + types**
```ts
import Fastify from "fastify";
import { z } from "zod";
import { ZodTypeProvider } from "fastify-type-provider-zod";

const app = Fastify({ logger: true }).withTypeProvider<ZodTypeProvider>();

const Query = z.object({ q: z.string().min(1) });

app.get(
  "/search",
  { schema: { querystring: Query } },
  async (req) => {
    return { q: req.query.q };
  },
);

await app.listen({ port: 3000 });
```

### TypeBox provider (recommended for OpenAPI + performance)

✅ **Correct: TypeBox schema**
```ts
import Fastify from "fastify";
import { Type } from "@sinclair/typebox";
import { TypeBoxTypeProvider } from "@fastify/type-provider-typebox";

const app = Fastify({ logger: true }).withTypeProvider<TypeBoxTypeProvider>();

const Params = Type.Object({ id: Type.String({ minLength: 1 }) });
const Reply = Type.Object({ id: Type.String() });

app.get(
  "/users/:id",
  { schema: { params: Params, response: { 200: Reply } } },
  async (req) => ({ id: req.params.id }),
);

await app.listen({ port: 3000 });
```

## Plugin Architecture (Encapsulation)

Use plugins to keep concerns isolated and testable (auth, db, routes).

✅ **Correct: route plugin**
```ts
import type { FastifyPluginAsync } from "fastify";

export const usersRoutes: FastifyPluginAsync = async (app) => {
  app.get("/", async () => [{ id: "1" }]);
  app.get("/:id", async (req) => ({ id: (req.params as any).id }));
};
```

✅ **Correct: register with a prefix**
```ts
app.register(usersRoutes, { prefix: "/api/v1/users" });
```

## Error Handling

Centralize unexpected failures and return stable error shapes.

✅ **Correct: setErrorHandler**
```ts
app.setErrorHandler((err, req, reply) => {
  req.log.error({ err }, "request failed");
  reply.status(500).send({ error: "internal" as const });
});
```

## Security Hardening (Baseline)

Add standard security plugins and enforce payload limits.

✅ **Correct: Helmet + CORS + rate limiting**
```ts
import helmet from "@fastify/helmet";
import cors from "@fastify/cors";
import rateLimit from "@fastify/rate-limit";

await app.register(helmet);
await app.register(cors, { origin: false });
await app.register(rateLimit, { max: 100, timeWindow: "1 minute" });
```

## Graceful Shutdown

Close HTTP server and downstream clients (DB, queues) on SIGINT/SIGTERM.

✅ **Correct: close on signals**
```ts
const close = async (signal: string) => {
  app.log.info({ signal }, "shutting down");
  await app.close();
  process.exit(0);
};

process.on("SIGINT", () => void close("SIGINT"));
process.on("SIGTERM", () => void close("SIGTERM"));
```

## Testing (Fastify inject)

Test routes in-memory without binding ports.

✅ **Correct: inject request**
```ts
import Fastify from "fastify";
import { describe, it, expect } from "vitest";

describe("health", () => {
  it("returns ok", async () => {
    const app = Fastify();
    app.get("/health", async () => ({ status: "ok" as const }));

    const res = await app.inject({ method: "GET", url: "/health" });
    expect(res.statusCode).toBe(200);
    expect(res.json()).toEqual({ status: "ok" });
  });
});
```

## Decision Trees

### Fastify vs Express

- Prefer **Fastify** for schema-based validation, predictable plugins, and high throughput.
- Prefer **Express** for minimal middleware and maximal ecosystem familiarity.

### Zod vs TypeBox

- Prefer **Zod** for app codebases that already standardize on Zod (forms, tRPC, shared types).
- Prefer **TypeBox** for OpenAPI generation and performance-critical validation.

## Anti-Patterns

- Skip request validation; validate at boundaries with schemas.
- Register everything in `main.ts`; isolate routes and dependencies into plugins.
- Return raw error objects; return stable error shapes and log the details.

## Resources

- Fastify: https://www.fastify.io/
- fastify-type-provider-zod: https://github.com/turkerdev/fastify-type-provider-zod
- @fastify/type-provider-typebox: https://github.com/fastify/fastify-type-provider-typebox



---
Source attribution: julio211916
Original project: https://github.com/julio211916/TlantiCAD-Studio-V0.1-alpha/blob/590aa4fe05d1ec71a02ee9cc76c9a20508b5bcea/skills/ju/skills/fastify/SKILL.md
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Mega AI Hub.

## Upstream license notice

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



# Mega AI Hub resource metadata

Creator / publisher: julio211916
Original project: https://github.com/julio211916/TlantiCAD-Studio-V0.1-alpha/blob/590aa4fe05d1ec71a02ee9cc76c9a20508b5bcea/skills/ju/skills/fastify/SKILL.md
Attribution basis: Source repository record

Fields of work: Development & Engineering, Product Management
Roles: Backend Developer, DevOps / SRE, Full-Stack Developer, Product Manager, Technical Product Manager
Specialties: API, Backend
Tools: Fastify, Typescript
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: a41bbd531d390701f4d5946788a6244a6aa7106a4535ac0731969b8625ed4629