In some implementations, a B+tree (b plus tree) can provide concurrent access to data while modifying nodes of the B+tree. In some implementations, a top-down B+tree can be provided where nodes of the B+tree can be proactively merged, rebalanced and split to prevent recursive operations moving up the B+tree. In some implementations, node (or page) record data can be merged to consolidate record entries within nodes of the B+tree while only locking 1-3 nodes of the tree at the same time. In some implementations, record data can be merged across multiple nodes of the B+tree. In some implementations, ranges of data can be removed from the tree while only locking 1-3 nodes of the tree at the same time. In some implementations, range of data can be replaced with new data while only locking 1-3 nodes of the tree at the same time.