B+ Trees (which store data at leaves) rather than B-Trees are what you want for good iteration performance usually.

An ordered B-Tree iteration would jump between different arrays in the tree often, but a B+ Tree would only have you jump to another array once you’re done iterating over all the elements in the current array.

The following article says the same. https://www.scylladb.com/2021/11/23/the-taming-of-the-b-tree....