This was answered in the comments section of the high scalability article [0]: > Deleting email (and generally any file) is not transactional. It can be rollba

This was answered in the comments section of the high scalability article [0]: > Deleting email (and generally any file) is not transactional. It can be rollbacked by server poweroff, for example. This can generate additional decrement, that is the problem. Generally, 2-phase commit between "email deleter" and "counter decrement" is not enough. You will also need 2-phase commit between "deleter" and physical disk(not its cache), and so on. Also, a network error can occur between this 2 phases. We do not want to lose user's data in any case. [0] http://highscalability.com/blog/2017/1/2/efficient-storage-how-we-went-down-from-50-pb-to-32-pb.html http://highscalability.com/blog/2017/1/2/efficient-storage-h...