We need a notification system for the platform. Here's what I'm thinking:

Real-time notifications via WebSocket - when something happens (new message,
payment received, task assigned) the user should see it immediately without
refreshing the page. Show a badge on the bell icon with unread count.

Also need email notifications for important stuff - payment confirmations,
security alerts (new login from unknown device), and weekly digest of activity.
Users should be able to configure which notifications they get via email vs
just in-app. There should be a preferences page for this.

Push notifications for mobile would be nice but can wait for v2.

For the backend: we need a notification service that handles routing - decides
whether to send in-app, email, or both based on user preferences and
notification type. Should be async so it doesn't slow down the main app.

Store notifications in a DB so users can scroll back through history.
Mark as read/unread. "Mark all as read" button.

Rate limiting is important - don't spam users with 50 notifications in
a minute if someone bulk-updates stuff. Batch them into a single
"X things happened" notification.

Tech stack: we use Python/FastAPI, React frontend, PostgreSQL, Redis for
caching. Already have SendGrid for transactional email.
