If they exist, they are running software written on either C or Rust, that can avoid memory efficiency traps and can schedule their workers on a more optimum way than a general purpose language.
That said, I'm not sure such thing exists. Just the memory overhead some common libraries impose on connections is enough to fill some 32GB.
Erlang works just fine for that many connections (depending on how much CPU you spend doing real work per connection). Socket buffers are tunable. 32GB isn't that much ram for a server, Android phones are shipping with 6gb, you can get 6TB into a server without getting too exotic.
Just to clarify : my knowledge on this is pretty deep so the only reason I didn't say "they exist" is that I don't personally have one in my DC (I've only managed up to 200k live connections). I know people very well who do. But yes of course the application would be written in some efficient language fit for the purpose like C, Rust, Go, Erlang. Probably not Java.
