RBAC or Notification System

Hi Design Gurus, Thank you for sharing your knowledge on design topics. It is a really helpful topic those are covered in the book. If possible please touch on RBAC and NotificationServices System design. These are a few among other projects which are necessary for each and every company and getting asked these days. Others are Authentication systems etc.

Course: Grokking the System Design Interview - Learn Interactively
Lesson: Designing Instagram - Grokking the System Design Interview

@Design_Gurus Please respond to this query.

Hi Team,
Hope everyone doing well. Any update on this?

I have more suggestions ( Please explain TCP, UDP, No. of Concurrent Connection made by any server in more detail). Because we know what is TCP or UDP. But how this is getting used in the actual design is what we should be able to understand.