CGI-based protocols transfer a bunch of metadata from the front end - such as the client IP address - without any injection or double-parsing vulnerabilities. Using HTTP twice means having more code and a greater security risk.
By the way if you're using nginx, then instead of FastCGI you might prefer SCGI, which does one connection per request and no multiplexing, so it's much simpler.
By the way if you're using nginx, then instead of FastCGI you might prefer SCGI, which does one connection per request and no multiplexing, so it's much simpler.