What exactly is remarkable about that? hn serves a couple thousand requests/s at most and is text only content. Which language/runtime *couldn't* do the same?
Is Arc still built on top of (formerly PLT Scheme, now) Racket? The Wikipedia page[1] says so. I'm more familiar with Common Lisp (which blazes) than Racket, but these seem like impressive stats to me.
Is it? HN is mostly static content. Ten years ago I wrote a simple web application using twister (python) that did well over a thousand requests per second. If we count just handling requests (and not churning out much data or doing anything fun processing) japronto for python claims to handle something like 1.2 million req/s on a single thread.
The most frequently access parts of the site are always in flux with users constantly adding, removing, and editing content.
I don’t know how you could statically generate that. At most, you could memoize the parts of the page that haven’t changed yet and return them without a complete lookup, but keeping that in synch with a database is not an easy problem.
You could regenerate the start page every 5s and comment pages whenever you need (new, edited or deleted comments) or every request if there has been more than 30s since it was last updated.
That would leave the serving to some of the applications being good at that (varnish?).
Finding the right heuristic regarding page regeneration might take some tweaking, but the amount of generating you have to do is small enough not to bother any single threaded program.
On a single server.
On a single core.