FastCGI: 30 Years Old and Still the Better Protocol for Reverse Proxies. Andrew Ayer di SSLMate spiega in occasione del 30° anniversario di FastCGI come il protocollo sia per certi versi (e almeno in teoria) migliore di HTTP per la comunicazione tra reverse proxy e backend.
FastCGI is very usable today, and has been in production use at SSLMate for over 10 years. That said, using a vintage technology has some downsides. It was never updated to support WebSockets. The tooling is not as good. For example, curl has no way to make requests to a FastCGI server. It supports FTP, Gopher, and even SMTP (however that works), but not FastCGI. When I benchmarked Go's FastCGI server behind a variety of reverse proxies, some workloads had worse throughput compared to HTTP/1.1 or HTTP/2. I don't think that's inherent to the protocol, but a reflection that FastCGI code paths have not been optimized as much as HTTP.