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Ticketmaster System Design
Visual Problem Diagram
Scenario
Taylor Swift tickets drop: 2M fans hammer 500 seats and your DB row lock on remaining=500 becomes a 30-minute outage. Fair queueing, inventory holds, and idempotent checkout separate a real ticketing system from "SELECT FOR UPDATE" on one row.
Design an event ticketing system where users browse events, select seats, and purchase under extreme contention. Flash sales are deliberately adversarial—queueing, sharded inventory, and holds are required.
You should support event catalog, seat maps, cart/hold, payment, and anti-oversell guarantees. Be ready to explain waiting rooms, hold TTL, and inventory sharding.
Constraints
Event listing, seat map, reserve/hold, purchase, payment hook, release expired holds
Zero oversell, fair admission under flash load, 99.99% for purchase path, hold TTL enforced
Millions users on sale start, thousands seats/event, 100:1 browse:buy ratio
Stages ahead
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