[HenryR]

A message queue is shared state. It may be more convenient shared state, and since it only needs to be got right once it might be more bulletproof shared state, but you have multiple threads that are serialising on access to a queue no matter how it is implemented.

[phintjens]

You're right that a message queue is shared state and has to be gotten right but that can be done (and ZeroMQ does it) without locks. It's thus invisible to application developers. You're wrong to say that multiple threads serialize on a queue no matter how it's implemented. ZeroMQ lets threads write full speed to a queue while another thread reads full speed from the queue, without wait states.