i configred nginx with gzip directives:
http {
gzip on;
gzip_types text/css application/javascript;
gzip_comp_level 9;
gzip_http_version 1.0;
gzip_proxied any;
}

some upstream servers have already gzipped the response, i see the lengh of the respense is similar to that send from nginx to client, i'm very curious to know if nginx just bypassed that response, zipped again or unzipped&rezipped it.