Step 7: Scalability and Performance

Picture 9:00 AM on a weekday. About 1 million reminders come due in the same minute, and the spike grows with the user base, because new users also pick 9:00. That one minute creates four separate problems:

1. The schedule holds 1 million rows for one minute, too many for one database partition.
2. The scheduler must read all of those rows and publish them within seconds.
3. The senders and providers cannot deliver 1 million messages at the same instant.
4. The spike lasts about one minute, which is shorter than autoscaling takes to react.