> Leaf nodes should not have "next" pointers In a standard B-tree, yes. PostgreSQL and MySQL, for example, use B-tree variants that have pointers between leaf

> Leaf nodes should not have "next" pointers In a standard B-tree, yes. PostgreSQL and MySQL, for example, use B-tree variants that have pointers between leaf nodes. Postgres is based on Lehman & Yao (itself a B+(*?) Tree variant), and InnoDB uses a B+ Tree with a next pointer.