Question Price of scaling with headless unity server

Hi, I am currently exploring backend solutions for multiplayer games.
I wonder how it scales using unity also in the backend as a server. Even with the server build settings, it takes computing sources and how does it play out for a large player base? For example lets say I have a card game with 20k (hard to achieve number, just to compare) ccu. How much source usage difference does it make in the backend side using unity vs creating a custom game server with something like go. Especially for ram, even an empty build server running instance takes about 100 mb ram. So I dont think it scales well in this perspective. And each game session means a new unity instance running if my understanding is not wrong? Any insights about this would be appreciated.

 

I personally don't know of any card game that runs a full blown Unity server or game engine on the server side. All the popular card games using Unity use a lightweight custom backend. Go, as you mentioned is pretty much ideal for this. How much faster will it be? That always depends on the specifics of course but I'd say you can expect at least a magnitude of better performance if not much more.