Problem is that the very definition of a cache is that you have the same thing in two (or more) places, which have to stay in sync. So blind adherence to DRY amounts to never using the technique of caching.
Its more a general guideline. In practice we break it all the time because it's not always possible or we may want to trade off for something else (performance in your case).
Though generally I think when we talk about DRY in the code style sense vs the data (source of truth) sense these are related but different.
However, even at Google there is a if_change_this_change_that lint rule to keep code changes between different files in sync. Meaning there's cases when you will have to define the same thing twice.
