@danberindei is right, you still need to locate the value to update and that's done with the key index. Again as @danberindei rightly says, given the design, which maximises lookup speed on overflowing caches, the use cases where `maxKeysInMemory` is really usable is very limited. The moment there's a risk of keys being evicted, limiting the keys in memory can result in a old entry leaking.