We are trying to act as a proxy for a site within the same DMZ. Things seem to work fine, except when there is quite a heavy load. There are many CSS assets that just hang upon retrieval. Sometimes the full page comes through; sometimes just spins forever.

Server: nginx 1.6.1 running on Linux.
Memory: 18Gb

proxy_buffering on;
proxy_buffers 256 8k;
proxy_busy_buffers_size 64;
proxy_temp_file_write_size 64;

Under heavy loads, about 1500 requests a second, a page is not completely sent back to the browser as some of the CSS resources taking anywhere from 2 - 10 seconds to return. It will just spin until eventually it gets sent back. CPU and memory usage is not dramatically high. Smaller sites return without any issue at all.

Do I have the buffering wrong or is there something else at play?

Thank you

Imran