A B+Tree's stable algorithmic performance relies on a single invariant: the path from its root to any leaf is always the same length. However, a delete operation can cause a node to underflow (falling below its minimum occupancy), triggering a rebalancing procedure to maintain this critical invariant. Modern B+Trees use fast, optimistic latching protocols which operate under the assumption that rebalancing happens rarely. The mere possibility of an underflow can force the rebalancing into the sl...