The page says visible_couriers_stale > 8% for 5m . Dispatchers see drivers frozen two streets behind their actual position, while the ingest graph still looks healthy. That combination is the first warning that scaling realtime fan-out publishing for event delivery has failed at the map: accepting location events is not the same as delivering a current view to every viewer.

The answer is to scale realtime fan-out publishing around bounded-staleness presence, not raw connection count. Partition by delivery area, coalesce replaceable positions, attach monotonic sequence numbers, and give reconnecting clients a snapshot-plus-replay path. Page on user-visible age and recovery failure. Queue depth belongs in the diagnosis, but it is a poor primary signal because a deep queue can contain obsolete coordinates that should never reach a screen.

This distinction matters outside logistics too.…