Design Flash Sale / Coupon Service — TikTok — Intervues

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Design Flash Sale / Coupon Service[ OK ] 310 — full content available
[ INFO ] category: System Design  difficulty: hard  freq: high  first seen: 2026-01-13
[HARD][SYSTEM DESIGN][HIGH]Distributed Systemswebmachine_learningSystem DesignmobileConcurrencyHigh Trafficbackendinfrastructure
$ cat problem.md
Design a server for a limited-time coupon/ticket service where users from different countries compete to claim coupons with equal probability.
Requirements:
Users from different regions/countries
Fair chance for all users regardless of location
Handle high concurrency during flash sales
Prevent overselling
Support millions of concurrent users
Key Components:
Global load balancing
Distributed rate limiting
Inventory management with distributed locks
Queue system for fairness
CDN for static content
Discussion Points:
How to ensure fairness across regions with different latencies?
Database choice for high-write scenarios
Handling network partitions
Anti-bot measures
Retry handling and idempotency
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