To add a background worker process, simply open your app's Processes tab and create a new process for the background worker.

For example, you can add Sidekiq by adding a process that has "bundle exec sidekiq" as the start command.

You'll want to make sure these background jobs are restarted each deploy so they run the latest code, so don't forget to check the restart box.

Processes are managed by Systemd so they will be restarted on crashes automatically.