So, why not just deliver that topology using off the shelf components? Rabbit, Kafka, ZeroMQ, ... the toolbox is deep. This is not meant as a criticism, I am

So, why not just deliver that topology using off the shelf components? Rabbit, Kafka, ZeroMQ, ... the toolbox is deep. This is not meant as a criticism, I am simply trying to understand what I am missing when I look at your design :-)