I am working on a jQuery Mobile Web App where a company will have the ability to message certain groups of users (based on their profile preferences).
I am debating on what is the most efficient way to mark when each user has read the latest messages. I have considered using a session to try and keep track of the last time they opened the messages page, and comparing that to the post times of the messages. I have also considered a table with the message_id and the user_id, marking each one as read when they open the page.
I think both would work, but I am trying to balance the pros and cons. Keeping in a database would allow me to keep a history (especially if i added a timestamp column to know when they read the message), but if it is going to hurt the app performance due to the table size, then it may not be worth it. The app will potentially have 10's of thousands of users.
One thing I should probably mention is that the users may use the app on multiple devices and the app will have very long session times, potentially allowing the user to stay logged in for months. I like the idea that if they read it on one device then it would mark it read on all devices, which may make sessions difficult to work with, right?