An apparatus comprising an input/output (IO) port configured to couple to a large-scale storage device, a memory configured to store a plurality metadata databases (DBs) for a file system of the large-scale storage device, wherein the plurality of metadata DBs comprise key-value pairs with empty values, and a processor coupled to the IO port and the memory, wherein the processor is configured to partition the file system into a plurality of partitions by grouping directories in the file system by a temporal order, and index the file system by storing metadata of different partitions as keys in separate metadata DBs.