I chose to use GitHub as the external system in this recipe because it is freely available to everyone and representative of typical requirements. In this recipe, our inbound ESG service needs to provide an API that will be invoked by the external system and conforms to the signature of the external system's webhook. We implement this webhook using the API Gateway and a webhook function. The single responsibility of this function is to transform the external event to an internal event and atomically publish it using event-first Event Sourcing.
Note that the external event ID is used as the internal event ID to provide for idempotency. The external event data is included in the internal event in its raw format so that it can ...
