> JSON is there for human to read a record of data by group.
That's what tree is for
> I think it is only good to use directory as data table to store JSON data files, but not for JSON data properties.
I see that as no better than one big JSON file or a normal NoSQL database.
If you're really fancy then the whole DB is just a VFS and those JSON files aren't real files, just a serialized form of the DB.