One question the article doesn't answer is: why are they cacheing at all? If your cache is that big it isn't a cache. How much bigger is the dataset in question? There are 250 billion entries. Assuming 80/20, that implies 1.25 trillion records?
What's the speed of service/response time relative to the data source?
At that point it might be enough to replace your multiple caches with fewer in-RAM databases?
What's the speed of service/response time relative to the data source?
At that point it might be enough to replace your multiple caches with fewer in-RAM databases?
It's an interesting problem.