A batch data-ingestion service writes a custom metric 'pipeline/records_processed' every 5 minutes when a cron-triggered job runs successfully. Recently the cron scheduler silently stopped firing, so the job never ran and no data points were written at all. Your existing threshold-based alert (fires when records_processed < 100) never triggered because the metric simply stopped reporting. You need an alerting policy that notifies the on-call engineer when the job stops producing the metric entirely. What should you configure?