Even on older systems that approach could scale quite a ways. Things like Perl with an expensive startup needed to do fancy preloading and preforking, and it was easy to mentally account that to the process of starting a process per CGI, but the vast majority of difficulty scaling that approach came from the incredibly heavyweight process of starting one of those processes. (Perl was convenient for CGI back in the day, but in a lot of ways was a bad choice in almost every other way. And I'm not talking about syntax at all here, I'm talking about all the characteristics of its startup and execution model. Python has almost identical problems, for instance.)

If you've got a tiny little C program that doesn't do much DLL loading and runtime linking, and is likely already in cache to be memmapped directly into a process, and is shoveling out content with little-to-no computation you'll have a website that'll take an HN'ing without even noticing even on old hardware.

"A tiny little C program" worries me on other fronts, but there's a reasonable selection of things that are safe enough to put on the internet and still compile to single fast binaries that you could use in 2022. Alas, the options were not so nice in 2005.