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This is one of those questions where you think you know it until you actually have to draw it out.
Start by clarifying requirements and scale (e.g., pages per second, storage needs, freshness). Then design a modular architecture covering URL frontier, fetcher, parser, deduplication, and storage, while discussing trade-offs like politeness, scalability, and fault tolerance.
Pro tip: Emphasize the importance of a distributed, fault-tolerant design with back-pressure and monitoring, and mention how you'd handle dynamic content and robots.txt compliance to show production maturity.
Ask about scale (pages/day), content types, freshness, and use case (search indexing vs. content analysis). Define functional and non-functional requirements.
Outline components: URL frontier, fetcher, parser, deduplication, storage, and scheduler. Explain how they interact and scale horizontally.
Detail the URL frontier (priority, politeness), fetcher (async I/O, rate limiting), parser (HTML parsing, link extraction), and deduplication (content hashing, Bloom filters).
Discuss partitioning, replication, fault tolerance, back-pressure, and monitoring. Explain how to handle failures and retries.
Compare design choices (e.g., push vs. pull, batch vs. stream), and mention optimizations like caching, compression, and dynamic content handling.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.