There's still a lookup hit of log-b32n versus contiguous memory immutable vector with O(1). Locality can also an issue with tree-like structures but muted with

There's still a lookup hit of log-b32n versus contiguous memory immutable vector with O(1). Locality can also an issue with tree-like structures but muted with the large branch factor. Of course the flip side scala gives you the kitchen sink for persistance.