Design an URL shortener system
that allows individual users to create and track clicks.
About this question
Category
System Design
Subcategory
User-Facing Platforms
Difficulty
Easy
Est. time
40 min
What this question helps you practice
This system design question tests how you build a user-facing platform that must be fast on redirects while still collecting useful analytics. A strong answer should separate the read-heavy redirect path from asynchronous click tracking and consider abuse, expiry, and custom aliases.
How to practice
Clarify core use cases
Define accounts, custom aliases, expiration, privacy, analytics granularity, and expected scale.
Design URL creation and redirect
Explain code generation, uniqueness, storage, caching, redirect status, and fallback behavior.
Add tracking and safety
Use async event logging, aggregation, bot filtering, rate limits, malware checks, and abuse reporting.
Strong answer signals
Keeps redirects fast using cache and a simple lookup path.
Separates click event ingestion from analytics aggregation and reporting.
Considers collisions, custom slugs, malicious links, rate limiting, and privacy.
Common mistakes
Making click analytics synchronous before redirecting the user.
Ignoring slug collision, enumeration, or abuse prevention.
Designing only storage tables without discussing latency and traffic patterns.
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