Right. The idea is that by having your database, message queue, and application all share the same transactional context, "reprocessing" the message twice doesn

Right. The idea is that by having your database, message queue, and application all share the same transactional context, "reprocessing" the message twice doesn't matter, because the effects are only ever committed exactly once. It's true that this doesn't work if your processing touches external systems or otherwise escapes the transaction context, but in those cases you do still get at-least-once delivery (or at-most-once, if you choose to commit the receipt before processing the message). It really is a powerful technology and when leveraged can absolutely reduce the level of effort and cognitive burden to building correct asynchronous systems.