Reminder Alert System: System Definition

A reminder alert system lets users schedule alerts. When an alert is due, the system delivers it through the channels the user picked: email, SMS, push notification, or an in-app message. It is one central service that stores every scheduled event and sends each message out on time.

Slack's reminder feature and calendar apps do the same job at a smaller scale. Slack runs scheduled jobs so each message reaches the user at the exact moment. Here we build the general version: a web-scale service that serves millions of users at the same time.

Key Terminology