What does Kafka return on front?

Question

API

Hello! I am building a model of user communication with a movie search service, they work + - as in the diagram below. I’m trying to understand in what form the response from the provider’s service comes to the front, tell me pliz !! (
Is this JSON? Kafka can pass JSON through itself? Or is it somehow processed on the back? I’m not looking for the exact answer how this whole scheme works, I just want to hear how someone thinks to enter yourself, thank you!!!)