Nginx has also formed the basis of CloudFoundry's routing tier, and this cloudfoundry.com and appfog.com. Nginx load balancing can be very simple, but you can customize it to your heart's content with Lua [1].

You can also use it for your application tier with Passenger, [U]WSGI, FPM, FCGI...

[1] https://github.com/cloudfoundry/cf-release/blob/master/jobs/...