Troubleshooting edge cache revalidation TTFB overhead on conditional GETs (HTTP/3 asset delivery)

15 days ago by media2url to c/webdev

Hey everyone,

I've been diagnosing asset delivery latency across edge nodes and noticed an unexpected TTFB spike during conditional 304 revalidations compared to fresh direct HTTP/3 requests.

Here is the DevTools network waterfall comparison for reference: https://files.media2url.com/...

While fresh asset fetches over HTTP/3 consistently complete sub-60ms, cache-lookup validation requests (Row 3) are introducing ~98ms of initial handshake overhead before confirming unmodified status.

For those running edge caching or CDN reverse proxies with stale-while-revalidate headers:

  1. Is an edge POP revalidation roundtrip usually this pronounced on warm caches?
  2. Have you found better latency improvements by tuning stale-if-error vs letting client-side Cache-Control handle immutability directly?

Curious to hear your setup experiences!

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