System Design Interview - Design a Web Crawler (Full mock interview with Sr. MAANG SWE)

In this mock interview, a seasoned software engineer designs a web crawler, detailing the intricacies involved. The discussion covers the crawler's core requirements such as scheduling, URL processing, and the prioritization of website types for effective crawling. Key aspects like avoiding duplicate content through advanced data structures like Bloom Filters and checksums for content verification are explored. The engineer also addresses non-functional requirements, emphasizing scalability and performance optimization, and outlines the potential for customization based on website behavior and content changes, ensuring a comprehensive approach to web crawling.

Chapters -
00:00 - Introduction to Web Crawler Functionality
01:12 - Exploring Key Web Crawler Components: Scheduler, Fetcher, and Politeness Policies
03:40 - Discussion on Crawling Policies: Frequency, Politeness, and Duplication Avoidance
07:22 - Enhancing Web Crawler Performance: Optimization and Capacity Planning
13:11 - Strategies for Efficient Scheduling and DNS Resolution in Web Crawling
22:32 - Techniques for Handling Duplicate Pages: URL Hashing and Bloom Filters
31:29 - Advanced Topics: Checksum Logic and Recrawling Mechanisms
39:16 - Setting Limits and Best Practices for Domain Crawling
41:09 - Conclusion and Final Thoughts

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[JeremeyNewton]

The scheduling insights are super helpful! Do you think using HasData would enhance performance for a large-scale web crawler?

[emikenester]

The insights on scheduling are spot on! Do you think using HasData could help simplify the implementation process?

[pranayguda]

Wait @27.00 How does hashing the URL and storing it Will reduce the Time Complexity to O(1) we still have to look for the Hash in DB right or are you putting that in an in memory db?

[AmitKumar-hnqh]

I don’t understand what point of doing maths if we don’t know how to comprehend those to number of cpu we use or scale. Just do math and say hmm this the storage we need to deal with 😮.

[WiktorJurek]

What happened at the 15 minute mark? Lots of stuff was skipped.

[ashrafabdelrasool]

object storage will decrease performance . i think we should go with instance store then sync in batch to object store

[narayancse]

Can you please tell me the tool being used by Ravi the candidate?

[fuadadio]

Great video. Thank you for these amazing contents.

[shyama]

I was just watching a video on bloom filter - spooky!