a fairly standard structure for storing this kind of data, so I will not describe it in detail - see a reference book on database design and algorithms for that

a generalised binary tree, for which there exist algorithms for inserting and deleting keys while keeping the tree balanced

a specialized multiway tree designed especially for use on disk

In computer science, a B-tree is a tree data structure that keeps data sorted and allows insertions and deletions in logarithmic amortized time. It is most commonly used in databases and filesystems.