Flash-Sale Ticket Booking

A concert-ticket platform releases 50,000 tickets at exactly 10:00 AM. Within seconds, hundreds of thousands of users attempt to purchase tickets simultaneously. The application must prevent two customers from purchasing the same seat. Checkout can take several seconds because payment authorization is performed by an external provider, and the company does not want to maintain a fleet of always-running application servers. If payment succeeds the reservation is confirmed; if payment fails or the customer abandons checkout, the seat should automatically become available again after 10 minutes. The architecture has to absorb sudden traffic spikes, prevent duplicate reservations, and avoid keeping a database connection open for every waiting customer.