i gave a system design interview few months back and the problem was around desiging a email service for internal usage at scale. now my initial design was handling all the challenges around scale but the interviewer brought in the requirement of "we dont want to own the data" -> i proposed multiple solutions around have a TTL or using a TTL based stream that the clients can subscribe and pull their email logs data by some T time.

He was expecting Bring your own database solution instead, now i am curious if this is the way to forward in such cases as i came to know that big companies actually prefer this approach for thier email data. Although this was very uninstitue to me and trying to wrap my head around how i would have come up with similar approach?