FYI, the final result is subject to change, but the current solution being tested works on the entire main IP.Board domain. Guests and logged in users.
Yes this works aslong as whatever http accelerator doesn't cache changed data.
The best method for this is uncaching cookie'd requests. (Logged in users) unless the backend can check periodically every few seconds for changes (smartly, less per other things or uncaching commony requested URIs) shoutbox and such will uncontrollably cache and show stale data.
When you cache using the options IP.Board has separately and enable main domain caches for agents with no logged in cookies for boards with public data commonly requested.
This is the best method and for most boards causes very low requests. Guest requests can be uncontrollable, most logged in users don't do insane req/sec so its mostly cached.
We did Varnish over LiteSpeed on a WHM/cPanel live production system with a few dozen clients and it almost dropped the load to sub 1 and no complaints for days. We switched back with no complains, when notifying clients they did notice a large performance increase.
for us Varnish instantly will saturate the connection between client and server vs litespeed/apache/lighttpd only saturating bit by bit till it's done.