Post Locking for Frontend

I was building a pretty complex application that allows users to modify page content using a front-end form. One of the things I needed to solve was preventing 2 people from modifying the page content at the same time. A quick Google search found this extremely helpful WordPress plugin:

https://github.com/sc0ttkclark/wp-post-locking/blob/master/skc-post-locking.php

Simply, it prevents two people from modifying the same page content at the same time. If a user is currently editing the content, it doesn’t allow another user to access it and it displays a message to the other user that the content is currently being modified.