API Response Caching and Compression
Speed up backend responses with in-memory and distributed caching layers, smart cache invalidation, and payload reduction so servers do less work per request.
API Response Caching and Compression is a free Web Performance Optimization & Lighthouse lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Web Performance Optimization & Lighthouse learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Why Cache on the Backend?
Recomputing the same response for every request wastes CPU and database time. Caching stores computed results so repeat requests return instantly, cutting both latency and load.
Layers of Caching
- In-process memory fastest, but per-instance.
- Distributed cache (Redis/Memcached) shared across servers.
- HTTP/CDN cache at the edge.
A Simple Cache-Aside Pattern
The most common pattern: check the cache, return on hit, otherwise compute, store, and return. This is called cache-aside.
async function getUser(id) {
const hit = await redis.get('user:' + id);
if (hit) return JSON.parse(hit);
const user = await db.findUser(id);
await redis.set('user:' + id, JSON.stringify(user), 'EX', 300);
return user;
}Choosing a TTL
A time to live balances freshness against hit rate. Volatile data needs short TTLs; reference data can live much longer. Always set some expiry to avoid stale buildup.
Invalidation Strategies
The hard part of caching is invalidation. On writes, either delete the affected keys or update them (write-through). Stale data here is a common production bug.
async function updateUser(id, data) {
await db.update(id, data);
await redis.del('user:' + id);
}HTTP Caching Headers
For cacheable API responses, set Cache-Control so browsers and CDNs can reuse them, removing the request entirely on a hit.
res.set('Cache-Control', 'public, max-age=60, stale-while-revalidate=300');Conditional Requests
ETag and If-None-Match let the server reply 304 Not Modified with no body when data is unchanged, saving bandwidth.
res.set('ETag', hashOf(payload));
// next time: if If-None-Match matches, send 304Shrinking the Payload
Return only the fields clients need, paginate large lists, and avoid over-fetching. Smaller payloads serialize faster and transfer quicker.
Compressing Responses
Enable gzip or Brotli on JSON responses. Combined with caching, this minimizes both compute and transfer per request.
const compression = require('compression');
app.use(compression());Avoiding Stampedes
When a hot key expires, many requests may hit the database at once (a cache stampede). Mitigate with locks, request coalescing, or stale-while-revalidate.
Strategy Summary
- Cache-aside with sensible TTLs.
- Invalidate on writes.
- Use Cache-Control and ETags.
- Trim and compress payloads.
- Guard against stampedes.
Quick Check
After a user updates their profile, the API keeps returning the old data for several minutes. What is the most likely cause?
Recap
You learned to cut backend work with layered caching (cache-aside, TTLs, invalidation on writes), HTTP caching via Cache-Control and ETags, payload trimming, and compression, while guarding against cache stampedes.
Frequently asked questions
Is the “API Response Caching and Compression” lesson free?
Yes — the full text of “API Response Caching and Compression” is free to read here on the web, and the Web Performance Optimization & Lighthouse course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Web Performance Optimization & Lighthouse course, upgrade to CoddyKit PRO.
What will I learn in “API Response Caching and Compression”?
Speed up backend responses with in-memory and distributed caching layers, smart cache invalidation, and payload reduction so servers do less work per request. You practise Web Performance Optimization & Lighthouse with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Web Performance Optimization & Lighthouse?
No prior experience is required. Web Performance Optimization & Lighthouse on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “API Response Caching and Compression” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Web Performance Optimization & Lighthouse lesson?
Yes. Every Web Performance Optimization & Lighthouse lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Backend Performance Bottlenecks
- Database Query Optimization
- Server-Side Rendering (SSR) Impact
- API Response Caching and Compression