I kind of disagree about the language. Not because I wouldn't want an implementation in a fast language, but because I think a well designed chat system must b

I kind of disagree about the language. Not because I wouldn't want an implementation in a fast language, but because I think a well designed chat system must be performant even if your language is an order of magnitude (or two) slower than it has to be. If you need to start throwing brute force at it, something's up with the design. Get the design right first and demonstrate it is right by showing that even a slow system has no trouble with it.