Staging anchor trees for improved concurrency and performance in page range index management

Anchor tree cross-merge within a distributed storage system. A computer system identifies a data structure that includes (i) a root anchor tree and (ii) an ordered set of anchor trees that are ordered based on their creation, such that a last anchor tree of the ordered set of anchor trees is most-recently created. The data structure stores index data for a set of objects stored in a non-volatile storage. The computer system creates a new anchor tree in the ordered set of anchor trees. The computer system identifies, from a set of delta tables, index data representing one or more objects that are stored on the non-volatile storage. The computer system merges the index data representing the one or more objects into the new anchor tree.