Packagecloud processes package deletion on a per-package basis. To increase the number of package deletions which can be completed in parallel, you can adjust your /etc/packagecloud/packagecloud.rb file and set the resque['delete_worker_count'] option to the desired number of concurrent deletion processes.

Keep in mind that deleting packages from a repository will cause a reindex job to be queued so that the repository metadata can be regenerated without the packages which were deleted. If you are deleting an entire repository by selecting "Delete repository" from your repository settings page, no reindexing will take place as the repository is being removed.