'Notifying users about expiring certificates (how to design?)

I want to create a way to notify users about expiring certificates that they may possess in a predetermined amount of time before it actually expires (ex. 1 week, 1 month, 6 months, etc). Are there any other ways to run this system other than using a cronjob that perhaps checks all stored certificates once a day to see what certificates are expiring soon? Or is this the industry standard?



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