Idempotent Output Keying for Long-Running Tasks During Rolling Deployments

A scheduled job that needs ninety to one hundred eighty seconds to produce a single output file looks harmless until the day you ship a new build while it is still running. The deployment controller drains the old task and starts a replacement. For a window of two or three minutes, both replicas are alive, both read the same input snapshot, and both intend to write the same logical output.