Design a Production-Ready URL Shortener
Overview
This question evaluates competency in designing a scalable, reliable, and secure production URL shortening service, covering API design, link data modeling and analytics, ID/token generation, caching and read/write paths, partitioning/replication/consistency choices, rate limiting and abuse mitigation, TTL handling and cleanup, and HA/DR and monitoring. Commonly asked in system design interviews to probe architectural trade-offs for high-read consumer services, it belongs to the System Design domain and emphasizes practical application of distributed systems and operational concepts rather than only conceptual theory.
System Design: Production-Ready URL Shortening Service
Goal
Design a production-ready URL shortening service that can issue short links, resolve them at low latency, and provide management and analytics. The service must be scalable, reliable, and secure.
Requirements
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Public APIs to:
- Create short links (optionally with custom alias and expiration/TTL).
- Resolve short links to their destination.
- Manage short links (enable/disable, update destination, extend TTL, fetch stats).
- Propose a database schema for links and analytics.
- Propose an ID/token generation strategy with collision avoidance.
- Describe read/write paths with caching.
- Discuss partitioning, replication, and consistency choices.
- Include rate limiting, abuse/spam mitigation.
- Include analytics and click tracking.
- Describe TTL handling and cleanup.
- Strategies for high availability (HA), disaster recovery (DR), and monitoring.
- Compare key trade-offs under different traffic patterns (read-heavy vs write-heavy, hot-spot links vs long-tail, single-region vs global).
Assume a consumer-facing scale with very high read QPS and moderate writes, and that links can be public or managed by authenticated users.
Solution
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