Keeping checkout independent of the ERP
The ERP needs every order, but it is slower and less reliable than the storefront; a synchronous call would tie checkout to the ERP’s uptime.
An afterPlace plugin publishes an order-created message to RabbitMQ; a separate consumer performs the ERP export.
Eventual consistency — an order can exist in Magento before the ERP sees it — plus a queue and consumer to keep healthy and monitored.