In page 62, it is mentioned that all the interactions are synchronous and that you modify the calls to the title service to be asynchronous for the sake of showing how to do it.
I wonder, why not use Kafka for the example, since in previous chapters it was already mentioned that calls to it where asynchronous? No need to make up contrived examples.
Creating Software with Modern Diagramming Techniques: Asynchronous interactions with Kafka (page 62)
Yup that’s an excellent idea, not sure why I didn’t pick that up when I covered async!