System Design - Notification System

In this wiki, we will explore an approach to designing a notification service.

Part of the System Design Case Studies series (7 parts)

1. System Design - Rate Limiter
2. Introduction to Consistent Hashing
3. System Design - Design Key-Value Store
4. System Design - Design a Unique ID Generator for Distributed Systems
5. System Design - Design a URL Shortener
6. System Design - Web Crawler
7. System Design - Notification System ← you are here

Requirements

• What type of notifications do we need to send? => Push, SMS, email
• Real-time system? => Soft real-time system. In case of high load, a slight delay is tolerable
• Supported devices? => iOS devices, Android devices, laptops, and desktops
• Who triggers notification => Any service, authenticated
• Opt-out feature? => Available to the users

Back of the envelope estimation:

• 10 million mobile push notifications, 1 million SMS, and 5 million Email notifications

Architecture

Architecture: notification system hld

Tracking:

• Monitor queued notifications
• Track failure events

Future Study:

• How JWT authentication is used?
• How to deduplicate notifications?