CDN и edge-кэширование: пример кода

# ✅ Static, content-hashed asset: cache hard at edge AND browser.
Cache-Control: public, max-age=31536000, s-maxage=31536000, immutable
# /static/app.7f3a9c.js

# ✅ Cacheable HTML with fast personalization window:
#   browsers revalidate; the CDN holds 60s and serves stale up to a day while refreshing.
Cache-Control: public, max-age=0, s-maxage=60, stale-while-revalidate=86400

# ✅ Per-user / secret: never let a SHARED cache store it.
Cache-Control: private, no-store

// Cache-key hygiene at a CDN edge worker: strip tracking params so
// /page?utm_source=x and /page are ONE cache entry (huge hit-rate win).
export default {
  async fetch(request) {
    const url = new URL(request.url);
    for (const p of ['utm_source', 'utm_medium', 'fbclid', 'gclid']) {
      url.searchParams.delete(p);
    }
    const key = new Request(url, request);           // normalized cache key
    const cache = caches.default;
    let res = await cache.match(key);
    if (!res) {
      res = await fetch(request);                     // MISS → origin
      if (res.ok) await cache.put(key, res.clone());  // populate edge
    }
    return res;
  },
};