A cold start after a failover

A promoted standby serving traffic with an empty cache and a cold opcode cache, measured during a drill.

  first request               2.4s
  p95, first 60 seconds       1,880ms
  p95, after 5 minutes          210ms

the warmer from 2025 runs on deploy and not on
promotion, because promotion is not a deploy.

added to the failover runbook as a step, which takes
four seconds and removes most of the first minute.

The warm-up script existed and was bound to the wrong event, which is the ordinary way a mechanism fails to apply — nobody had thought of promotion as a case that needs warming. Four seconds in a runbook against sixty seconds of degraded service, discovered in a drill rather than in a failover.