Web Crawler

Design Web Crawler.

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Patterns

  • Crawler Pattern

Expected topics

  • Web Crawler
  • Crawler Pattern
  • worker
  • content
  • FIFO queue
  • crawler trap
  • politeness
  • domain
  • Bloom filter
  • false positive

Self-check prompts

  • What users, scale, latency, availability, and consistency requirements should you clarify for Web Crawler?
  • What are the main APIs, data model, and request flow?
  • Where is the main bottleneck around Crawler Pattern, worker, content, and how would you scale it?
  • What failure mode matters most, and how do retry, recovery, and idempotency work?
  • Which trade-off would you choose, what do you lose, and when would you change that decision?

Common mistakes

  • Jumping into vendor names before clarifying requirements and scale.
  • Listing components without explaining the end-to-end request flow.
  • Leaving the bottleneck vague instead of quantifying capacity, partitioning, and recovery behavior.
  • Mentioning trade-offs without choosing an option and explaining the condition that would change the decision.