Basically when an article is being created/edited, then its category gets checked_out.
I can see that when a category is being edited by a user in the backend then their user ID gets inputted into that category's "checked_out" field in the DB.
See screenshot: https://www.dropbox.com/s/zq4y7qqgalhtosv/Screenshot%202015-05-06%2010.47.01.png?dl=0
So instead of creating "an independent table in the database called “lock_table”, fields can be id_contenttype, lock, date, user_id…" and then "When the first user clicks on “new", make the" category "checked_out" field value the user ID. Is this possible?