When I destroy tenants in preview (I do not know if it is only a preview thing or also related to production because I didn't have time to investigate about this), I regularly see the following error in the logs, although the tenant gets destroyed aftet the hierarchy chain:

{"_aj_globalid"=>"gid://system/ServiceContract/1409617817692"}, ["Hierarchy-Account-2445582574503", "Hierarchy-ServiceContract-1409617817692"], "destroy"
ActiveRecord::RecordNotUnique: Mysql2::Error: Duplicate entry '245-6' for key 'index_mail_dispatch_rules_on_system_operation_id_and_account_id':
INSERT INTO `mail_dispatch_rules` (`system_operation_id`...

I attach the whole logs (I think it is complete in this file).

Dev Notes

If we can avoid accessing the MailDispatchRules, knowing that we are gonna delete the whole tenant, that's better. If not, we may be stuck in an 'infinite' loop in the find_or_create for a race condition, in that case, we may have to add a lock to only access it once at the same time.