alt Hacker NewsWeb / API services during bursts. Or just when you _really_ don't want to scale horizontally.
Elixir / Golang can do this very well. And they do. I have supervised, led and authored such projects that are in production to this day.
Rust too but it's lower-level and you kind of have to hand-roll OTP which of course will always fail.
from experience, during bursts it's never actual web/api server that is bogged down, it's the downstream io bottlenecks.
if your accepting layer is abstracted away and implemented correctly, there is very little performance difference between different concurrency approaches and all you're exposed to as developer is implementation of your handler functions.