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

• Public APIs to:
  1. Create short links (optionally with custom alias and expiration/TTL).
  2. Resolve short links to their destination.
  3. 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.