The difference between a supply chain integration run with synchronous REST API calls and a data flow based on an asynchronous, Transactional Outbox architecture is the difference between the production line stopping or keeping on running. In classic monolithic structures or hastily written microservices, sending an HTTP POST request to an external supplier system and waiting for a "200 OK" is the most common design mistake. When the external API fails to respond for 15 seconds or the connection