I have a simple fastcgi responder that converts a JSON post to a CSV download. It works in a streaming fashion, writing the response before finishing reading the request. According to the FastCGI specification, such operation is allowed: http://www.fastcgi.com/devkit/doc/fcgi-spec.html "The Responder application sends CGI/1.1 stdout data to the Web server over FCGI_STDOUT, and CGI/1.1 sby jkl - Nginx Mailing List - English