Schedules and timers

Three tools, from the smallest:

• A sleep inside a run: await ctx.sleep("cool-off", "10m"). Durable: a crash or a deploy during the ten minutes changes nothing.
• A delayed start: engine.start(report, "report-7", input, { delay: "1h" }) (or at: date). The run exists under its ID from now; result() waits through the delay.
• A schedule: a run on every cron time or interval, until you delete it.

A scheduleCopy Anchor Link

const s = await engine.schedule(
  "nightly-report",
  { cron: "0 2 * * *", timezone: "Europe/London", overlap: "skip" },
  report,
  { recipients: ["ops@example.com"] },
);
await s.pause(); await s.resume(); await s.trigger();
await s.backfill(new Date("2026-11-01"), new Date("2026-11-07"));
await s.delete();

fusee schedules ls, fusee schedules pause nightly-report and the UI's Schedules screen do the same from outside.

What it guaranteesCopy Anchor Link

• Each time runs once. A run's ID is the schedule's name and its time (nightly-report@2026-11-09T02:00:00Z), and a start attaches to a run that has the ID. Two processes, a crash during the start, a backfill over a time that already ran: still one run per time.
• Missed times catch up. After downtime, the times missed within catchupWindow (default a year) start, oldest first. Set it to an hour for a job where only the latest matters.
• Overlap is a choice. skip (the default) skips a time while the previous run still runs; buffer-one keeps one waiting; allow-all starts every time; cancel-other cancels the running one first.
• Time zones. A cron in Europe/London fires at 02:00 local time across daylight-saving changes; a time that does not exist that night is skipped, one that happens twice runs once.
• Jitter spreads starts of many schedules over a window (recorded, so the same on replay).

A schedule is itself a workflow (fusee.schedule/<name>) running the same native code in every SDK, so it has no scheduler process to deploy and keeps working through restarts and failovers.

ChoosingCopy Anchor Link

The scheduled job example runs in five languages.