NGINX [Engine-X] is an HTTP(S) server, HTTP(S) reverse proxy and IMAP/POP3 proxy server written by Igor Sysoev. It has been running on many heavily loaded sites, including Facebook, Zappos, Groupon, LivingSocial, Hulu, TechCrunch, Dropbox, Tumblr and WordPress.
Lightweight HTTP reverse proxy dispatching requests differently based on a hash of the IP address of the client. Either to different upstream servers or by adding tags in the HTTP headers. It is used as a seamless implementation of A/B testing. For instance, the user can simply deploy two versions
... [More] of his/her applications and make 10% of the traffic go to the first and 90% to the latter. [Less]