> The pseudo-LRU redis used to have is appropriate for very high-speed caches (it's essentially a 5-way associative cache), but is so very not appropriate when going out to disk, where the access latency is horrible.

Redis is an in-memory database, so what's the problem?

Also, keep in mind that it has to fit in 24 bits, so not all solutions are possible, even if they are theoretically better