Do people use zeromq for this kind of work? It seems the various socket types are tailored to building such load balancing and routing architectures, but I'm not aware if zeromq is in use at this scale.
Yup, we use ZeroMQ for internal routing for this kind of thing. Each instance of our edge server (Pushpin) binds on a SUB socket to receive messages destined for external clients. This makes it possible for internal publishers (using PUB) to route among edge servers using a brokerless mesh.
