Could you say more about how a non-network socket would be beneficial? I'm guessing simpler code and lower resource usage, but I'm curious what you're interested in. And by "single node", do you mean one server / one user (even if the user is, say, a single API consumer or whatever), or something else?

Any euid can connect to a localhost tcp socket. But a unix socket is protected with filesystem permissions (rwxrwxrwx, etc.).