1. A computer implemented method for providing a graph database which contains another graph database, comprising the steps of: providing a master database; providing at least one replica database core comprising an identity of said master database; providing a concentric replica database to said replica database core to store any relatively long-lived data which relates to said replica database core; for each transaction in a replica stream, producing an equivalent set of writes and applying them to said concentric replica database; wherein said concentric replica database comprises a superset of said master database.