I would want to serve the homepage with a cached version of the page for both logged in and new users. And then to use Ajax to update the content appropriately, for example if the user had already vote up a post, the relevant button would be different than otherwise.
As I am new to wordpress, I wonder is there any way or appropriate plugins to achieve this goal.
Alternatively can I use Ajax to update only some part of the page, e.g. Post meta on the present page?