Design a Ticket Booking System

Requirements

A ticket booking system lets many people pick specific seats for a show or train, pay for them and receive a confirmed ticket. The hard part is that thousands of people want the same few seats at the same moment.

Functional:

• Browse shows or trains and see which seats are free.
• Select seats and hold them for a few minutes (a temporary reservation).
• Pay, then receive a confirmed booking.
• Release held seats automatically if payment does not finish.
• Cancel and refund.

Non-functional:

• Never sell one seat twice. This is the one rule that cannot bend.
• Survive a flash sale: a popular show opens and a huge crowd arrives together.
• Seat map reads can be slightly stale; booking writes cannot.
• Fair: do not let bots or fast connections take everything.