HN does, because pg and rtm liked it from way back, we inherited it, and it works well.

If you don't mind, can you list HNs entire stack: OS, external web server, app language, db?

The OS is BSD. Everything else is Arc IIRC.

I've seen nginx failures recently, so there might be a nginx reverse proxy hanging out in front of Arc (the whole stack noticeably behind CloudFlare, too, but that's sort of beyond the original question).

That'd be how I'd build it, if I'm right. Doing webby things without nginx is like forgetting pants, to me.

Excuse my ignorance, but what is "Arc"?

The current[1] distribution comes with a hn clone, that as far as I know, is mostly equivalent to the code that used to power hn at some point in the not too distant past.

[1] current might not be the best name for it, but as far as I can tell it a) works, b) has been ported to Racket (as opposed to being trapped on some ancient version of PLT Scheme), and c) is maintained (ish): https://github.com/arclanguage/anarki