Design a Web Crawler (also asked as BFS / DFS coding)

System DesignGoogleLast reported August 2026Low Frequency
Reported
2× across candidate reports
First seen
May 2026
Last reported
August 2026
Reported outcome
unknown

Problem Overview

Google system design question, reconstructed from 2 candidate reports (May 2026 to August 2026). Candidates reported 7 follow-ups.

  • 7 candidate-reported follow-ups — the probes candidates report being asked, with the trigger for each
  • The full 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. Follow-ups candidates reported, not invented ones.
Codex Fact-Checked
Technical claims, formulas, and scale numbers are reviewed against primary sources.
Interviewer Follow-ups
The follow-ups candidates reported, with the trigger that prompts each one — plus the mistakes that sink people.
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