I'm interested to know what happens when there is a failure or a deployment? Having static servers handling load is only part of the problem in our experience. The true complexity and scalability of a system comes when you consider how it copes under load with unexpected failures (network, hardware), but more importantly expected maintenance such as regular deploys, scaling up and scaling down events. Do you have any metrics for that? Those are the problems we've been focussing most of our energy on at Ably (https://www.ably.io), not just message per second rates which is often not really the problem.