Upserts are more powerful because the client can always generate a new uuid to get the POST behavior you desire, but the reverse is not the case: there is no st

Upserts are more powerful because the client can always generate a new uuid to get the POST behavior you desire, but the reverse is not the case: there is no straightforward way to safely retry timeouts, partial success, side effects, etc. You say the same request has a different impact on the system, but what that means is the system converges to the requested state. Maybe this is overkill if your retry strategy is to have a user in the loop, but I don't see how it's simpler for the client even without any retry behavior (if/else new/reuse uuid vs if/else put/post).