Cron check-ins incorrectly marked as timed-out despite successful SDK sends

[InterstellarStella]

Environment

SaaS (https://sentry.io/)

Steps to Reproduce

1. Configure a cron monitor in AWS Lambda using @sentry/aws-serverless:

const monitorConfig = {
  schedule: { type: "crontab", value: "0 3 * * *" },
  checkinMargin: 1,
  maxRuntime: 5,
  timezone: "Etc/UTC",
};

export const handler = async (event) => {
  await Sentry.withMonitor("cleanup", async () => {
    // job logic (~30s runtime)
  }, monitorConfig);
  await Sentry.flush();
};

2. Run the Lambda (manually or scheduled)
3. SDK debug logs confirm both check-ins sent successfully:

Sending checkin: cleanup in_progress
Sending checkin: cleanup ok

Expected Result

Check-in shows as successful/OK in the Sentry UI.

Actual Result

Check-in marked as timed-out with tooltip: "This check-in was incorrectly marked as timed-out. The check-in was processed late due to abnormal system latency in Sentry."

Link to the monitor in the internal Linear ticket.

Product Area

Crons

Link

No response

DSN

No response

Version

No response

[linear]

ENG-6942

[getsantry]

Assigning to @getsentry/support for routing ⏲️

[getsantry]

Routing to @getsentry/product-owners-crons for triage ⏲️

[andrianvaleanu]

That "system latency" error is annoying since the logs prove your Lambda did its job correctly. If the backend keeps lagging and marking your runs as failed, you might want to try a simple uptime tool like Pulsetic https://pulsetic.com/ instead, though it won't give you the same deep trace data.