drush queue-list
to see a list of queues and how many are lined up in each
there's also
drush queue-run
drush sqlq "DELETE FROM queue WHERE name='message_subscribe'" is the only way to clear a queue
references: https://drupal.stackexchange.com/questions/17750/how-do-i-clear-or-dele…
https://www.sitepoint.com/drupal-8-queue-api-powerful-manual-and-cron-q…
https://knackforge.com/blog/vamsi/how-create-queue-woker-drupal-8