A system includes storage of data into a target memory location allocated to a target leaf node of a tree-based index structure, the target leaf node being a child node of a parent node of the tree-based index structure, where the tree-based index structure comprises one or more other leaf nodes which are child nodes of the parent node, and each of the target leaf node and the one or more other leaf nodes is associated with a plurality of allocated memory locations, incremental identification of all unused allocated memory locations between a first allocated memory location of a left-most one of the target leaf node and the one or more other leaf nodes and a last used allocated memory location of a right-most one of the target leaf node and the one or more other leaf nodes, and movement of data stored in the target leaf node and the one or more other leaf nodes into the identified unused allocated memory locations.