HTTP/3 at the edge, and nothing behind it

Enabling QUIC on the edge terminator changes the client leg and nothing else, which is worth being clear about before reading a benchmark.

the path:

  browser  ──HTTP/3──▶  edge  ──HTTP/1.1──▶  origin

what changes:      connection setup, head-of-line blocking
                   on a lossy network, migration across
                   a network change
what does not:     origin latency, database time,
                   application time — which is 92% of ours

measured, mobile, p75 first byte:  410ms → 380ms

Thirty milliseconds on the p75 is a real improvement and it is a rounding error against a 400 ms server render, which is the honest framing. The case where it matters is a lossy connection with several parallel requests, and the archive’s traffic is mostly one document and a few assets — the benchmark that sells this feature is not the one that describes this site.