As for (2), there may be a chance of conflict in theory, because vpop
commands do not implement the mechanism to avoid the concurrent access.
But, in the real world, it is the rare case that the same folder is
created/deleted at the same time.
When would you create a user and delete them at the exact same time?
Either the user exists or doesn't. Whatever state you end up in is
probably sane, and odds are you won't do multiple actions as each depend
on the opposite state.
Thank you for your detailed explanation.
In the DB world, the concept of transaction is essential.
But, as you pointed, it is not true for vpop commands.