Got the system design prompt for an interview. I understand messenger SD but never seen these requirements. Anyone can help with it?

Question:
For a new book club feature, your task will be to design a chatroom that supports weekly ~1hr chats.
Within these chatroom, the members will discuss this week's audiobook at a pre-determined time.
Assume the scheduling and creation/management of book clubs are already taken care of.
Please use pen & paper / a virtual whiteboard to walk me through a system design for the chat feature.
I am looking for defining the MVP, walking through the main components, and scalability of the solution.