Send several Serialized Java objects under one Kafka Topic

Hello All,
I'm working on proof of concept for sending several Java Objects
under one Kafka Topic. More about the requirements:
https://stackoverflow.com/questions/65811681/design-kafka-consumers-and-producers-for-scalability

I managed to implement this working concept:
https://github.com/rcbandit111/skyobject_engine

In this code example I send several Java Objects under one Kafka Topic
and response is sent back into another Kafka Topic.

I would like to ask you what are the advantages and disadvantages in
this design of sending data between Consumer and Producer? I want to
use a serialized Java object, not JSON because I think it's more
optimized for performance.

Can you share your feedback, please?

Also is there some better way to implement this? Like for example
using Streaming API?


BR,
Peter