Design a URL Shortener

Design a URL shortening service similar to Bit.ly or TinyURL.

The system should allow users to submit a long URL and receive a shortened version that redirects to the original. Consider how to generate unique short codes, store mappings, and handle high read traffic.

Context

URL shorteners are one of the most common system design interview questions. They test your understanding of hashing, storage trade-offs, and API design fundamentals.

Requirements

•Given a long URL, generate a unique short URL
•Redirect users from the short URL to the original long URL
•Short URLs should be as compact as possible (6–8 characters)
•Support custom short URLs (optional alias)
•Track basic analytics: total clicks per short URL

Non-Functional Requirements

•Read-heavy system: 100:1 read-to-write ratio
•Redirect latency < 50ms (p99)
•URLs should not expire by default
•System should handle ~1,000 new URLs/day, ~100K reads/day

Constraints

•The system serves a single geographic region (no global CDN required)
•Authentication is not required for creating short URLs
•No need to support editing or deleting URLs after creation

Evaluation Criteria

Evaluation criteria and weights will be revealed after you submit your solution. This ensures a fair assessment of your design skills.

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