I'm building a high-traffic site and want to reduce origin load with edge caching

Great goal. Edge caching can dramatically cut origin traffic, reduce latency, and absorb traffic spikes—especially for high-traffic sites.

What to cache at the edge

Best candidates:

• Static assets: images, CSS, JS, fonts, video thumbnails
• Public HTML pages that don’t change every request
• API responses that are safe to share across users
• SSR pages with short TTLs or stale-while-revalidate
• Redirects and error pages that are frequently requested

Avoid caching:

• Personalized pages
• Authenticated responses unless carefully varied
• Highly dynamic data that must be fresh per request

Core caching strategy

A strong pattern is:

1. Cache static content aggressively

   • Long TTLs
   • Fingerprinted filenames, e.g. app.3f2c1.js
   • Use Cache-Control: public, max-age=31536000, immutable

2. Cache HTML carefully

   • Short TTLs or stale-while-revalidate
   • Example: Cache-Control: public, max-age=60, stale-while-revalidate=300

3. Use surrogate/edge caching headers

   • If your CDN supports it, set separate cache controls for browser vs edge
   • Example concepts:
     • Cache-Control for browsers
     • CDN-Cache-Control or surrogate headers for edge

4. Vary correctly

   • Only vary on what truly changes the response
   • Overusing Vary reduces cache hit rate
   • Common pitfalls: Cookie, Authorization, Accept-Language

5. Serve stale on origin issues

   • Use stale-while-revalidate or stale-if-error
   • This improves resilience during origin slowdowns

Practical header examples

Static asset

Cache-Control: public, max-age=31536000, immutable

HTML page

Cache-Control: public, max-age=60, stale-while-revalidate=300, stale-if-error=86400

API response

Cache-Control: public, max-age=30, stale-while-revalidate=60

Key implementation considerations

• Cache key design: path + query string + select headers
• Purge/invalidation: decide whether to version assets or actively purge
• Compression: cache separate compressed variants if needed
• Observability: track hit ratio, origin offload, TTFB, stale serves
• Protection from cache fragmentation: normalize URLs and strip irrelevant query params

Common mistakes

• Caching pages with cookies by default
• Including unnecessary query params in the cache key
• Short TTLs on static assets
• No purge strategy
• Forgetting to test cache behavior across deployments

A good starting policy

If you want a simple, effective baseline:

• Static assets: cache 1 year, immutable
• Public HTML: cache 1 minute with stale-while-revalidate
• APIs: cache only if responses are shared and safe
• Use versioned asset names and a purge mechanism for HTML/content updates

If you want, I can help you design:

1. a CDN caching policy,
2. specific cache headers for your stack (Cloudflare/Fastly/Akamai/Nginx), or
3. a cache key and invalidation strategy for your app.