How to properly organize the data model?

Question

MongoDB

There is a model: Room - it has an array of messages and an array of participants. It is necessary that the room has a field with the number of new messages for each user.
How can this be properly organized?
While there is an idea, to associate each message with a participant and mark whether the participant read the message or not? But there will be too many connections. Maybe someone has already solved a similar problem and will tell you the best solution?

Answer 1

If messages are read sequentially, then it is possible to store for each user the id of the last read message. Anything with a large id is considered unread.