In a sharded cluster it may be possible for two database drops to happen on two different shards at the same time. Since a database does not have a UUID or a documentKey, the resume token for the drop will simply contain a timestamp. This means that is possible for two distinct changes to have the same resume token.

A database drop will invalidate the stream, so this likely isn't an issue, but if we allow an actual notification of this event without an invalidation, then a client who tries to resume with one of the two identical resume tokens might see a drop twice or not at all.