Abstract: A data storage system stores historical statistical data in a statistics hierarchy that is a tree of nodes. The data storage system receives a metric request from a remote requesting device through a Representational State Transfer (RESTful) Application Programming Interface (API), including a metric path that is a delimited list of list elements separated by delimiter characters. In response to an aggregation special character in the metric path, the data storage system i) obtains a category name immediately preceding the aggregation special character in the metric path, ii) identifies a branch of the statistics hierarchy indicated by the category name, iii) aggregates values of leaf nodes contained in the branch of the statistics hierarchy indicated by the category name that match a leaf type in the metric path to generate an aggregated value, and iv) transmits a metric response containing the aggregated value to the remote requesting device.