The NATS philosophy on guaranteed delivery is that <i>delivery</i> isn&#x27;t what you care about, its the <i>action</i> taken as a result of delivery.  If the far end system receives your request but crashes before processing it, was it really received? The business logic of most applications requires end-to-end acknowledgement of transactions, so NATS considers that an application problem.<p>(Disclaimer: I work for Apcera)