# Fastify — Fast & Low Overhead Web Framework for Node.js

> Fastify is a fast and low overhead web framework for Node.js, focused on providing the best developer experience with least overhead and a powerful plugin architecture. Schema-driven with JSON Schema validation built in.

## Install

Save the content below to `.claude/skills/` or append to your `CLAUDE.md`:

## Quick Use

```bash
npm i fastify
```

```js
import Fastify from "fastify";
const app = Fastify({ logger: true });

app.get("/", async () => ({ hello: "world" }));

app.post("/users", {
  schema: {
    body: {
      type: "object",
      required: ["name"],
      properties: { name: { type: "string" } },
    },
  },
  handler: async (req) => ({ created: req.body }),
});

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

## Intro

Fastify is a fast and low overhead web framework for Node.js. Benchmarks consistently show it handling 30K+ req/s — among the fastest Node frameworks. Built around schema validation (JSON Schema) and a lightweight plugin system.

- **Repo**: https://github.com/fastify/fastify
- **Stars**: 36K+
- **Language**: JavaScript
- **License**: MIT

## What Fastify Does

- **HTTP server** — built on Node http with optimized routing (find-my-way)
- **Schema validation** — JSON Schema for body/params/query/headers
- **Serialization** — fast JSON output via fast-json-stringify
- **Plugin system** — encapsulated context with `fastify-plugin`
- **Hooks** — onRequest, preHandler, onSend, onResponse lifecycle
- **Logging** — Pino by default (fastest JSON logger)

## Architecture

Plugin tree: each plugin creates an encapsulated context. Decorators attach state to request/reply/instance. Schema compilation happens once at startup for zero-cost runtime validation.

## Self-Hosting

```bash
# Production
NODE_ENV=production node server.js

# Docker
FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production
COPY . .
CMD ["node", "server.js"]
```

## Key Features

- ~2x faster than Express in benchmarks
- Native TypeScript types
- JSON Schema validation + serialization
- Request lifecycle hooks
- Plugin encapsulation
- HTTP/2 support
- Async/await first-class
- Graceful shutdown built-in

## Comparison

| Framework | Req/s | Schema | TS |
|---|---|---|---|
| Fastify | ~45K | JSON Schema | Yes |
| Express | ~15K | Manual | Optional |
| Koa | ~25K | Manual | Optional |
| Hapi | ~20K | Joi | Good |

## FAQ

**Q: Can it replace Express?**
A: Yes. The `@fastify/express` compatibility layer supports most Express middleware.

**Q: Why is it so fast?**
A: Optimized routing (radix tree) + compile-time schema serialization (fast-json-stringify) + Pino logging.

**Q: Can NestJS use Fastify?**
A: Yes. NestJS officially supports a Fastify adapter that replaces the default Express.

## Sources & Credits

- Docs: https://www.fastify.dev
- GitHub: https://github.com/fastify/fastify
- License: MIT

---
Source: https://tokrepo.com/en/workflows/fastify-fast-low-overhead-web-framework-node-js-267271ae
Author: AI Open Source