Déjà Vu

Friday's deploy gave the billing worker a memory leak and is now stuck in a reboot loop. It eats RAM until it falls over, restarts and gets back to work. The queue in front of it guarantees delivery, so the crashes cost nothing anyone could see. Support saw it Monday: customers charged twice for the same order. The queue delivered every payment it was given. Twice, when it felt unsure. The Job: Make every order charge exactly once. The queue promises at least once. Those are two different promises.

Free to play, no account needed. A deterministic engine grades your design against this scenario's SLA - error rate, latency, and cost.