A special feature of this load balancer (besides the fact that it's written completely in Python): it doesn't use multiple processes or threads, instead it uses asynchronous I/O. This allows many connections to be handled simultaneously in just one thread, which keeps the system load much lower than classical balancers that start a process or thread for each connection. It uses either Twisted or the asyncore module that comes with Python. And the whole thing is also blazingly fast - for example, the same approach is used in Medusa, a web server in Python that comes close to Apache's performance when serving static HTML pages. Here's the original article.