[zzzcpan]

> The problem is, all those on shared hosting can't handle 100 concurrent users without crashing.

This is not a configuration problem though, but a shared hosting problem. Most of the modern shared hosting is no longer a shared hosting. Instead, each client gets a tiny slice of server resources and never more, not even for a day. Their rationale for this is to host more clients on the same server. And they seem to be ok with clients leaving if their websites went down because of this. Some even make money selling such solutions, like cloudlinux.