It's reasonable to delay deleting encrypted data (which can take a long time) and just delete its keys (which is very fast) upon a user request to delete the da

It's reasonable to delay deleting encrypted data (which can take a long time) and just delete its keys (which is very fast) upon a user request to delete the data. If you believe in encryption, then once you delete the only remaining copies of keys, the encrypted data is as good as deleted. So that's why it's a great idea to implement data deletion as a two-phase sequence of synchronous key deletion, then asynchronous low-priority block scrubbing (or marking free for reclamation). But not handling the case where your system is confused whether the keys are deleted (versus just temporarily unavailable) is less of a great idea.