How Ticketmaster Prevents Double-Selling Seats During High-Demand Onsales

When a major event goes on sale, hundreds of thousands of users simultaneously compete for a limited number of seats, creating a classic concurrency problem. Ticketmaster addresses this by placing a short-lived, atomic hold on a seat the moment a user selects it, preventing others from claiming it during checkout. The hold is written to the database as a conditional update, ensuring only one request can transition a seat from available to held at any given time. If a user abandons checkout, an expiry timer automatically releases the seat back into the pool. A virtual waiting room further protects backend systems by admitting users in controlled batches during traffic spikes, prioritizing correctness over speed to ensure no seat is ever sold twice.