# Request & Reply Objects — Fastify: Building High-Performance Node.js APIs

Source: https://www.skillbyai.com/en/fastify/ff-request-reply

> Use the request and reply objects to read params, queries, headers and bodies and send responses.

## request and reply

`request` contains the incoming HTTP request details (URL, headers, body, params, query). `reply` is an object with methods to send the response—it's pooled for performance.

## Reading request data

Access path params, query strings, headers, and body from the request object.

```javascript
fastify.get('/users/:id', async (request, reply) => {
  const { id } = request.params;
  const { filter } = request.query;
  const token = request.headers.authorization;
  
  return { userId: id, filter, hasToken: !!token };
});
```

## Sending replies

Return an object (auto-serialized to JSON) or use `reply` methods for custom status codes and headers.

```javascript
fastify.post('/items', async (request, reply) => {
  // Auto-JSON serialization
  return { id: 1, status: 'created' };
});

fastify.delete('/items/:id', async (request, reply) => {
  // Custom status and location header
  return reply.status(204).send();
});
```

## Return or send, not both

In an async handler, either `return` the payload or call `reply.send()`. Doing both logs a warning about the reply being already sent.

Quick check

**Quiz:** Which sets a status code and sends JSON in one chain?

- [x] `reply.code(201).send({id: 1})`
- [ ] `request.code(201)`
- [ ] `reply.json(201)`

*Answer:* `reply.code(201).send({id: 1})`. `reply.code()` returns the reply, so `.send()` chains.