System Design: URL Shortener

System DesignOpenAILast reported April 2026Medium Frequency
Reported
5× across candidate reports
First seen
November 2025
Last reported
April 2026
Reported outcome
mixed

Problem Overview

Design a URL shortening service (like bit.ly or TinyURL). Given a long URL, generate a short, unique alias that redirects to the original URL. The system must handle high read/write throughput, ensure uniqueness of short codes, support low-latency redirects, and be horizontally scalable. Topics typically…

  • 5 candidate-reported follow-ups — the exact probes interviewers asked, with the trigger for each
  • The rest of the problem statement — full requirements, constraints, and edge cases
  • Approach and trade-offs — what passing candidates did, and the mistakes that sink people
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Verified Source
Every question is reconstructed from multiple independent candidate reports. Verbatim follow-ups, not invented ones.
Codex Fact-Checked
Technical claims, formulas, and scale numbers are reviewed against primary sources.
Interviewer Follow-ups
The exact follow-ups reported by candidates, with the trigger that prompts each one — plus the mistakes that sink people.
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