A request is received from a client for accessing a first backup instance of first backup data associated with the client, wherein the request includes a first filename and a first savetime. A first directory record database is identified from a plurality of directory record databases based on a client identifier (ID) identifying the client. A first node identifier associated with a first directory comprising the first filename from the first directory record is identified. A first node record database is identified based on the first savetime from the node record databases, the first node record database including node records, each corresponding to a file or a directory of files associated with the first backup instance. A first node record is obtained from the first node record database based on the first node identifier. Node record information associated with the first node record is returned to the client.