Build BookMyShow

• Model cities, theatres, screens, movies and shows; a show is a movie on a screen at a start time with a price per seat category
• Browse: list movies in a city, shows for a movie in a city, and the seat map of a show with each seat's status (available, held, booked)
• holdSeats(showId, seatIds, userId) reserves the seats for a limited time (for example 5 minutes), all or nothing: if any requested seat is unavailable none are held; the hold returns an id and expiry
• Holds expire automatically through an injectable clock, returning seats to available; an expired hold cannot be confirmed
• confirmBooking(holdId, paymentToken) calls a payment stub; on success the seats become booked and a booking id is returned; on payment failure the hold stays until it expires or is released
• Concurrency safety: two users requesting overlapping seats at the same time never both succeed (explain the mechanism)
• cancelBooking releases the seats; a user cannot hold or book more than a maximum number of seats per show

Only after every requirement works.

• Pricing rules by seat category and time of day
• Waitlist or notification when held seats are released
• Idempotent confirmation, so retried payment callbacks do not double-book