A hash index allows you to determine which bucket an arbitrary key is mapped to without having to look anything else up.
That means you don't load it into memory at all, you just jump to Bucket[Hash(KEY)] and then check there for KEY (it may or may not be there due to false positives and the bucket being full).
That means you don't load it into memory at all, you just jump to Bucket[Hash(KEY)] and then check there for KEY (it may or may not be there due to false positives and the bucket being full).