@mariusor local recipients is another story. My internal database structure has nothing at all similar with ActivityPub, it instead follows user-facing presentation.

The primary problem I want to solve is that in Mastodon world, only the instance that hosts the post has a complete list of accounts that liked it. It's a bit better with reply threads, but boosts break everything, and, again, because of how mentions work here, only the OP instance has the complete threads.