Timers and timeouts in Temporal serve fundamentally different purposes: timers implement business logic (wait, then act), while timeouts detect failures. The post walks through Temporal's four Activity timeout types — Start-To-Close, Schedule-To-Close, Schedule-To-Start, and Heartbeat — explaining when and why to use each. It warns against using Workflow-level timeouts for business logic, since they terminate Workflows server-side with no chance for cleanup code to run. Key practical advice includes always setting Start-To-Close or Schedule-To-Close on Activities, using heartbeating for long-running Activities to avoid zombie Workers, and replacing Workflow timeouts with in-Workflow timers whenever the application needs to react to a time limit. A decision cheat sheet maps common scenarios to the correct tool.
