Architecture for notification or announcement system for web application

I have a dashboard for employees, I want to make announcement or notification system where admin can easily send information or update. I can easily achieve it by showing banner with title of the announcement and "Click here" button at the end that will open model/pop-up with Detail of the announcement. This is an easy to implement solution but it will create problem when there are multiple announcements going on at the same time.

Alternate to this is a notification system like Facebook or Stackoverflow. This solution is scalable as we can add more types of notifications like system generated. I am looking for both UX and code architecture suggestions. I am up for firebase, mysql, DynamoDB or any other option. Please suggest what is the best architecture for the same.

Below are the key features:

1. Scalable

2. Admin can send announcement to all users, to specific team or a specific user.

3. Clicking on the notification may open model/popup or a link.

4. Obviously has the count of new notifications/announcement for each user.