Direct server return means that traffic from the client to the server goes through Pen, but the traffic from the server to the client does not. There are a number of advantages to doing it this way, especially when it comes to performance – the load balancer never has to touch the return traffic. There are disadvantages as well, for example the load balancer cannot do SSL termination and the servers need special configuration.
Very, very early development, but it already kind of works. Ignore the mediocre performance, the code is running with debug level “blazing madness”.