INCIDENT-4471  checkout-worker
================================

19:02  Queue depth on checkout-worker begins climbing from a steady ~200 to
       ~4,900 over eleven minutes.
19:06  p99 latency on POST /checkout crosses 30s; the client-side timeout is
       30s, so callers start seeing failures.
19:09  Worker process RSS flat. CPU flat at 40%. No restarts, no OOM kills.
19:13  Upstream payment provider reports normal latency from their side.
19:20  Depth still rising. No dropped messages: every enqueued job is still in
       the queue, so nothing has been lost — the workers are simply not
       draining it.

Deploys in the window: none. Config changes in the window: none.
