[d--]

It turns out that most caching algorithms we use in practice (CDNs, memcached, storage, etc.) are still pretty far from the optimal hit ratio/ miss ratio.

See, e.g., recent work that exposes that gap (I'm an author)

https://www.cs.cmu.edu/~dberger1/pdf/2018PracticalBound_SIGM...

https://github.com/dasebe/optimalwebcaching