Design a Ticketmaster-like ticketing system

System Design Prompt

Design an online event ticketing platform (Ticketmaster-like) that allows users to:

1. Browse/search events and view seat maps (or ticket inventory).
2. Select seats (reserved seating) or ticket quantity (general admission).
3. Checkout and pay.
4. Receive a confirmed purchase (tickets/QR codes).

The system must handle flash-sale traffic (e.g., popular concerts) where many users attempt to buy the same limited inventory at the same time.

Requirements

Functional

• Event discovery: list events, event details, seating/availability.
• Purchase flow:
  • Temporarily hold seats while a user checks out.
  • Confirm purchase after successful payment.
  • Prevent overselling / double-booking.
• Cancellations/timeouts: seat holds expire and inventory returns.
• Basic anti-abuse: rate limiting / bot mitigation hooks.

Non-functional

• High availability during on-sale.
• Low latency for browsing; correctness (no double-sell) for checkout.
• Scalability for spikes (hundreds of thousands to millions of concurrent users).
• Auditability and supportability (logs, reconciliation).

Deliverables

Walk through:

• APIs
• Data model
• Core architecture and key components
• Concurrency control strategy for seat holds and purchase
• Caching, queues, and failure handling
• Key metrics and operational considerations