In-app notifications
Your task
Design an in-app notification system for a small product (the bell icon with a list of 'someone commented on your post', 'you were mentioned', etc., and an unread count). A few thousand users. When an event happens, the relevant users should see a new notification and an updated unread badge. Describe the data model and how the unread count stays fast.
It covers
- In app notifications
- Fan out
- Read state