Chicago Boss is fully asynchronous, using one single process to handle hundreds or thousands of simultaneous requests, and thus it solves the classic c10k problem. All other web frameworks will break down and cry if you ask them to process more than a few dozen simultaneous requests on a single machine. Chicago Boss is built with Erlang, the same platform used by banks and telecoms to achieve unprecendented scalability and (no exaggeration) 99.9999999% reliability.