Modifying an index for a database is provided. An index tree for the database is traversed by: identifying a next node in the index tree, requesting a lock of the next node in the index tree, responsive to locking of the next node in the index tree, releasing a lock of a current node of the index tree, and making the next node in the index tree the current node of the index tree, until the current node of the index tree is a leaf node of the index tree. Responsive to determining to split the leaf node, the lock of the leaf node is released and, after releasing the lock of the leaf node, a lock of a non-leaf node parent of the leaf node in the index tree is requested.