Not caching the questions and answers makes sense to me, as I imagine the hit rate wouldn't be terribly good. I would guess, though, that they somehow cache things like the sidebar list of blog articles, featured items, "Hot Network Questions", etc.
They do in fact cache some things like that, they've had caching issues in the past (and again recently, I think) with the wrong cache being used in some situations:
Comments
Not caching the questions and answers makes sense to me, as I imagine the hit rate wouldn't be terribly good. I would guess, though, that they somehow cache things like the sidebar list of blog articles, featured items, "Hot Network Questions", etc.
They do in fact cache some things like that, they've had caching issues in the past (and again recently, I think) with the wrong cache being used in some situations:
https://meta.stackexchange.com/a/235277