Problem: Users want instant notification without notification flooding.
Examples: Send a text message when an unhandled exception is thrown, but only 1 per day. When a new loan request form is submitted send an email, unless an email was sent in the past hour.
Solution: Store the datetime of the last sent notification and check it before sending a new notification.
This simple solution is often forgotten and replaced by a service that polls solution. I like Notification without Flood much more because you can use the existing application without requiring creation of a service.