Your question is Flight Booking System with Notifications. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Design a flight booking system with email + notifications: notification at booking, reminders at 72 hrs, 24 hrs, and 4 hrs before journey, configurable notification service with database-driven scheduled intervals
Asked in the Round 3 HM system design stage. Explain the practical architecture, persistence model, scheduling workflow, delivery guarantees, and failure handling.
