/api-response-optimization

---
name: api-response-optimization
description: Optimizes API performance through payload reduction, caching strategies, and compression techniques. Use when improving API response times, reducing bandwidth usage, or implementing efficient caching.
license: MIT
---

# API Response Optimization

Reduce payload sizes, implement caching, and enable compression for faster APIs.

## Sparse Fieldsets

```javascript
// Allow clients to select fields: GET /users?fields=id,name,email
app.get('/users', async (req, res) => {
  const fields = req.query.fields?.split(',') || null;
  const users = await User.find({}, fields?.join(' '));
  res.json(users);
});
```

## HTTP Caching Headers

```javascript
app.get('/products/:id', async (req, res) => {
  const product = await Product.findById(req.params.id);
  const etag = crypto.createHash('md5').update(JSON.stringify(product)).digest('hex');

  if (req.headers['if-none-match'] === etag) {
    return res.status(304).end();
  }

  res.set({
    'Cache-Control': 'public, max-age=3600',
    'ETag': etag