Thanks for your feedback! The article is really about service-to-service communication, not about front-ends or user-facing APIs. I changed the first sentence of it to make it even clearer. For the frontend-to-service or client-to-service communication, I consider REST or some other from of HTTP based a given. As a (human) user, I want to base my communication on commands and queries, and do want responses. But the services that generate those responses should not have runtime dependencies on other services. Instead they should interoperate in an event-driven way.