Saw this on Hacker News a short while back and it was pretty easy to set up. Might be pretty close to what you're looking for. It aims to be a sort of a replacement for what Electron does, without embedding a full browser.
~1/3 second is perfectly acceptable to me to be within the range of "real time", and is quick enough that I'd be willing to bet most people won't notice even in a two way conversation.