To summarise, nginx!

There was a small window where everyone was trying to move off Apache/mod_perl etc, coming up with all sorts of ways to talk to the backend faster… but then nginx walked into the chat and killed the 10k problem along with having its easy but fancy upstreaming, and that was that.

Nginx made horizontal scaling a winch, and because of that rewriting your backend to handle HTTP and FastCGI etc was more effort than it was worth.