Event-driven systems, written carefully, and running on capable hardware, are hard to beat on performance metrics. This is why node.js is so popular these days.
Interestingly, this was the programming model used by the Inktomi Traffic Server (http://en.wikipedia.org/wiki/Tra…), which smoked all competitive benchmarks for proxy servers when it ruled the roost during the last dot-com boom.
But what a difference a decade makes.
Building an event-driven infrastructure is hard