yep. but at least in the rdbms case, and probably in all cases, a flag (and an index on it) tends to be essential for query performance since the state of the flag will appear in most, if not all queries.

that's okay though, queries that reference the timestamp can be slow since they're housekeeping.

if the goal is the ability to rollback a certain delete, it's probably better to make it a nullable fk on a delete event with a timestamp.

But a nullable timestamp could also be viable, just can't tell two different delete, at the same time, apart

to bulk recover only x >= y ?