If you're doing thread-per-request, than no. If you've got an event-driven I/O system backed by a thread pool for executing parallel requests, than yes.

I set up a Rack adapter through Jetty 7 on JRuby that works exactly like this. The SelectChannelConnector is event-driven I/O, and the QueuedThreadPool handles requests in parallel.

The result? 6k req/sec on my laptop for a simple Rack app, basically the same as what's shown in these examples, since my machine is quite a bit slower, and I've clocked 10k/sec on faster machines.

(By the way, if you're interested, the Rack handler is in a gem called 'mizuno', and is at http://github.com/matadon/mizuno)