nginx/Windows uses the native Win32 API (not the Cygwin emulation layer). Currently only the select method is used as a notification method, therefore you should not expect high performance and scalability. Because of this and some known issues nginx/Windows is considered as a beta version. There is almost full-functionality in nginx/Windows as compared with the Unix version, except XSLT filter, image filter, GeoIP module, and embedded Perl language.