I'm working on a website which only registered users can access, and they are manually added to the site, since there is no registration enabled. Think of it as a private shop. The number of users is below 1000.
Each of the users can set a couple of events, such as birthday. They usually add less than 10.
I want to inform the user by email about their events, when there is a couple of days remaining to reach that event.
Now the question is, is it performance-wise better to run a single cron job every day at 00:00 and loop through all users and check their events ( stored as metadata ), or should I set a yearly cron job for each event of each user ( which ends up in having a thousand of cron jobs )?