When collections with different average sized documents (x,2x,3x,4x,5x) but having same number of documents within them the cache is behaving differently than expected. Before the eviction takes into place the distribution of the cache for the data is as follows. ( The collections are accessed in the same frequency and the memory is smaller than the collections)

This is the expected behavior as bigger sized documents mean bigger memory footprint. But, after the cache eviction takes place the distribution of the cache is as follows.

This means the eviction policy is evicting more of the bigger collection and giving priority to smaller ones (the opposite trend)