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