Fastify

Fastify’s JSON schema validation pipeline and low overhead make it one of the fastest Node.js frameworks available. Its plugin system with automatic dependency injection ensures encapsulation and reuse across large applications. Full TypeScript support and a Swagger plugin make it popular for building typed, self-documenting APIs. It’s the recommended replacement for Express when performance matters.

Quick start

npm install fastify

// server.js
import Fastify from 'fastify'

const app = Fastify({ logger: true })

const postSchema = {
  body: {
    type: 'object',
    required: ['title', 'body'],
    properties: {
      title: { type: 'string' },
      body: { type: 'string' },
    },
  },
  response: {
    201: {
      type: 'object',
      properties: {
        id: { type: 'integer' },
        title: { type: 'string' },
        body: { type: 'string' },
      },
    },
  },
}

const posts = []

app.get('/posts', async () => posts)

app.post('/posts', { schema: postSchema }, async (request, reply) => {
  const post = { id: posts.length + 1, ...request.body }
  posts.push(post)
  return reply.code(201).send(post)
})

await app.listen({ port: 3000 })

When to use

Fastify is the best drop-in upgrade from Express when you need better performance and built-in schema validation. Its plugin system scales better than Express middleware for large applications. For teams using TypeScript, Fastify’s schema-to-type generation reduces boilerplate significantly. If you’re starting fresh and want even more structure, NestJS can run on Fastify underneath. For edge/serverless environments, Hono is even lighter.