Design Ticket Booking Auto Release

Q: Design Ticket Booking Auto Release

This question evaluates system design competencies including distributed systems, data modeling, concurrency control, state machines, timeout/expiration mechanisms, and external payment integration within ticket inventory management.

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Question

System Design: Auto-expiring Ticket Reservations

Problem

Design a ticket-booking system where a reserved ticket automatically returns to the inventory if payment is not completed within 30 minutes.

Discuss and propose a design for:

Data model and state machine.
Reservation and payment flow.
Concurrency control to prevent overselling.
Timeout processing (auto-expiry) at scale.
Consistency guarantees and failure handling.

Assumptions

Tickets can be either seat-based (assigned seats) or general admission (GA) with a capacity count.
A reservation places a temporary hold for 30 minutes. If payment is completed within that window, the reservation becomes a purchase; otherwise, it expires and inventory is released.
High read/write throughput; horizontally scalable services.
Payment is processed by an external provider and can succeed/timeout/arrive late.

Design Ticket Booking Auto Release

System Design: Auto-expiring Ticket Reservations

Problem

Assumptions

Solution

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