[nickjj]

> zero if cache is hot (but 20 cache queries)

Rails lets you fetch_multi which means it would be 1 cache query if you used this feature.

> It is only a win if DB is the bottleneck

View rendering is pretty slow in Rails, rendering a view ends up being a real bottleneck. That's partly why caching that at the view layer is beneficial.

If Rails were able to cache templates as well as other frameworks then I would agree that in a lot of cases you wouldn't need to worry about it and could preload most things.