Reminder Alert System: Detailed Component Design

6.1 Scheduling Algorithm and Reminder Execution Pipeline

The Scheduler Service turns a stored reminder into a message at the right time. It is a distributed cron engine, a program that runs jobs at set times. It is built on the data model from Step 5. Here is how it works.

Scheduler instances and coordination. We run several Scheduler instances to handle the volume. No two of them may ever pick up the same reminder. So we split the work using the keys from Step 5: the time bucket and the segment.