I think this is the best answer right now. Just build your forum the way you would do it normally and aggressively cache. One addition I would make. Don't cach

I think this is the best answer right now. Just build your forum the way you would do it normally and aggressively cache. One addition I would make. Don't cache HTML, cache JSON responses, and build your forum as a one page app. This will allow you to have every response cached while still having customized pages per user (i.e. you could have a user profile on the page that shows a thread).