I found the whole rap genius thing overblown. The idea that a single request should block a server until it returns is absurd, given that it probably is spending most of its time waiting on io. If you really need to load balance CPU bound tasks you should do it properly with a work queue rather than expecting your reverse proxy to do it. Its true their docs got out of date, but i found their response "we'll help you design your apps properly for the 21st century" reasonable, even though they got slammed for it.