How do I approach System Design interview questions?

System Design questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master system design interviews.

What difficulty level is this interview question?

This is a hard difficulty System Design question, commonly asked during Technical Screen rounds at Anthropic.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at Anthropic during technical interviews.

Scale crawler with thread pool | Anthropic Interview Question

Quick Overview

This question evaluates system design and concurrent programming competencies, focusing on bounded thread-pool architecture, thread-safe frontier and deduplication structures, per-host politeness and in-flight limits, reliability mechanisms (timeouts, retries, backoff), and graceful shutdown and termination semantics.

Concurrent Web Crawler — Bounded Thread Pool, Thread-Safe Frontier, Dedupe, Politeness, and Trade-offs

You are refactoring an existing single-threaded crawler to run concurrently. Design the system and explain key concurrency and reliability concerns.

Requirements

Concurrency & Backpressure
- Run crawling with a bounded thread pool. Explain worker lifecycle, how work is acquired, and when workers/threads terminate.
Thread-Safe Data Structures
- URL frontier (work queue): thread-safe, prevents head-of-line blocking, and supports backpressure.
- Visited set: thread-safe deduplication with atomic test-and-set semantics.
Politeness & Reliability
- Per-host rate limiting and max in-flight requests per host.
- Timeouts and retries (transient failures) with backoff.
Control & Shutdown
- Support cancellation and graceful shutdown.
- Define termination/quiescence conditions when the crawl is "done."
Design Alternatives & Analysis
- Compare coarse-grained locks, fine-grained locks, lock-free/concurrent data structures, and message-queue based designs.
- Analyze trade-offs in contention, throughput, fairness, and memory usage.

Assume a single-process, multi-threaded crawler (language/runtime of your choice). Provide concise pseudo-code and justify design choices.

Quick Overview

Requirements

Concurrency & Backpressure

Run crawling with a bounded thread pool. Explain worker lifecycle, how work is acquired, and when workers/threads terminate.

Thread-Safe Data Structures

URL frontier (work queue): thread-safe, prevents head-of-line blocking, and supports backpressure.
Visited set: thread-safe deduplication with atomic test-and-set semantics.

Politeness & Reliability

Per-host rate limiting and max in-flight requests per host.
Timeouts and retries (transient failures) with backoff.

Control & Shutdown

Support cancellation and graceful shutdown.
Define termination/quiescence conditions when the crawl is "done."

Design Alternatives & Analysis

Compare coarse-grained locks, fine-grained locks, lock-free/concurrent data structures, and message-queue based designs.
Analyze trade-offs in contention, throughput, fairness, and memory usage.

Assume a single-process, multi-threaded crawler (language/runtime of your choice). Provide concise pseudo-code and justify design choices.

Scale crawler with thread pool

Quick Overview

Concurrent Web Crawler — Bounded Thread Pool, Thread-Safe Frontier, Dedupe, Politeness, and Trade-offs

Requirements

Solution

Comments (0)

Scale crawler with thread pool

Quick Overview

Concurrent Web Crawler — Bounded Thread Pool, Thread-Safe Frontier, Dedupe, Politeness, and Trade-offs

Requirements

Solution

Comments (0)