%db -> key1 -> [ [field1, field2, field3, field4]
                 [field1, field2, field3, field4]
                 [field1, field2, field3, field4] ]
    -> key2 -> [ [field1, field2, field3, field4] ]
    -> key3 -> [ [field1, field2, field3, field4]
                 [field1, field2, field3, field4] ]