A computer-implemented method of executing a query in a network of data centres, the method comprising a preparation stage and an execution stage; wherein the preparation stage includes: each data centre providing information relating to data centre parameters and/or proximity, allowing arrangement of the data centres in a dynamic hierarchical cluster topology of a parent data centre and child data centres, each child data centre having its own local data sequence which is to be processed by individual analysis tasks of the query, the child data centres together forming a cluster of similar and/or proximate data centres, the cluster having a single parent data centre; and the execution stage includes: the parent data centre sending the tasks to the child data centres and the child data centres sending to the parent data centre a sequence of outcomes derived from the local data sequence and the tasks; wherein both a child data centre and its parent data centre cache executed tasks executed by the child and the sequence of outcomes of the tasks executed by the child data centre.