Essentially, you can do whatever you like with these systems, and you do not have to take care about the scaling because if one server is overloaded, it just forwards the message to the next server, even if it were designated to a specific server. It weeds out the messages according to the load. If you want to scale it, you just add new servers.
It's a complex product because you have many degrees of freedom to connect different parts together. Whether it's sensible or not, is up to you, but the machine does allow it. But because of the vast degrees of freedom, it's complex.
