Designing a Ticket Booking System

Two people tap "pay" for seat H14 at the same moment, for the same screening. Exactly one of them must get it.

That sentence is the whole design. Everything else in a ticket booking system is arranged so the database itself can refuse the second person.

What the system must do

List venues and halls, and the seats inside each hall.

Schedule screenings: a movie, in a hall, starting at a time.

Show a seat map for one screening, marking which seats are already taken.

Take a booking for one or more seats in a single screening.

Take a payment for that booking.