Design a Ticketmaster-like ticketing system
Company: Affirm
Role: Software Engineer
Category: System Design
Difficulty: easy
Interview Round: Onsite
## 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
Quick Answer: This question evaluates system design and distributed-systems competencies for an online event ticketing platform, focusing on scalability, concurrency control for inventory and seat holds, API and data-model design, fault tolerance, and operational observability.