I just have a really shit server

which is great for human scale! Don't serve billions and burn the planet doing so.

Or the person never expected more than a couple of hundred concurrent users and dimensioned the container or whatever after that.

I once wrote a similar chat, but much much worse in many ways, that could easily handle thousands of concurrent users, but hosted it on a 1mbit residential line. When Slashdot hit it I stood no chance.