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Optional in single-runtime and composable images. Workers require resource definition using upsun resources:set, same as application containers. For more information, see how to manage resources. Workers are exact copies of the code and compilation output as a web instance after a build hook. They use the same container image. Workers can’t accept public requests and so are suitable only for background tasks. If they exit, they’re automatically restarted.
The keys of the workers definition are the names of the workers. You can then define how each worker differs from the web instance using the primary application properties.Each worker can differ from the web instance in all properties except for:
  • build and dependencies properties, which must be the same
  • crons as cron jobs don’t run on workers
  • hooks as the build hook must be the same and the deploy and post_deploy hooks don’t run on workers.
A worker named queue that was small and had a different start command could look like this:
Last modified on March 18, 2026