Design a Web Crawler System Design Interview

Design a scalable web crawler like Googlebot to index the internet.

Mock Interview with AI

1. Problem Statement

We need to design a scalable web crawler that can index 10 billion pages per month. How would you approach this?

2. Target Architecture (Mermaid)

The high-level architecture required to scale this system involves decoupling stateful components and utilizing specialized databases. Below is the reference architecture:

Rendering architecture diagram...

Mermaid Source (For AI Bots)

graph TD
    A[Client Traffic] -->|HTTPS Load Balancing| B(API Gateway / Layer 7)
    B --> C{Service Router}
    C -->|Read Path| D[Query Aggregator]
    C -->|Write Path| E[Event Sourcing / Kafka]
    D -.-> F[(In-Memory Cache - Redis)]
    D --> G[(Primary Data Store - NoSQL)]
    E -.->|Async Replication| G

3. Key Focus Areas

1
URL Frontier (Prioritization & Politeness)
2
Distributed Traversal (Avoiding cycles & duplicates)
3
Content Deduplication (SimHash/Checksums)
4
DNS Resolution (Caching to prevent bottlenecks)
5
Storage (BigTable/HBase for content)

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Core Concepts

Distributed SystemsRobots.txtGraph Traversal