API Response Optimization
Reduce payload sizes, implement caching, and enable compression for faster APIs.
Sparse Fieldsets
// 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
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
});
res.json(product);
});Response Compression
const compression = require('compression');
app.use(compression({
filter: (req, res) => {
if (req.headers['x-no-compression']) return false;
return compression.filter(req, res);
},
level: 6 // Balance between speed and compression
}));Performance Targets
| Metric | Target |
|---|---|
| Response time | <100ms (from 500ms) |
| Payload size | <50KB (from 500KB) |
| Server CPU | <30% (from 80%) |
Optimization Checklist
- Remove sensitive/unnecessary fields from responses
- Implement sparse fieldsets
- Add ETag/Last-Modified headers
- Enable gzip/brotli compression
- Use pagination for collections
- Eager load to prevent N+1 queries
- Monitor with APM tools
Best Practices
- Cache immutable resources aggressively
- Use short TTL for frequently changing data
- Invalidate cache on writes
- Compress responses >1KB
- Profile before optimizing