Identify and mitigate deduplication program risks

Q: Identify and mitigate deduplication program risks

This question evaluates understanding of system design and practical engineering competencies required for building resilient file deduplication tools, covering filesystem semantics, error handling, hashing and collision considerations, concurrency, performance bottlenecks, cross-platform interoperability, and safety trade-offs.

Q: 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.

Q: What difficulty level is this interview question?

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

Q: What role is this question designed for?

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

Question

System Design: Robust File Deduplication in the Real World

Context

You are designing a file deduplication tool that scans large directory trees on one or more filesystems, identifies duplicate files by content, and safely deduplicates them (e.g., by deleting extra copies, replacing them with hard links, or using copy-on-write reflinks). The tool must be resilient to real-world issues.

Prompt

What problems can a file deduplication program encounter in real-world use, and how would you mitigate them? Address each of the following, providing concrete strategies and trade-offs:

Permission and I/O errors
Files changing during the scan (TOCTOU)
Path length limits and path normalization
Symlink loops and mount/device boundaries
Memory and disk bottlenecks while indexing and hashing
Hash function choice and collision risks
Partial vs. full hashing and final verification
Concurrency, scheduling, and throttling
Incremental rescans and checkpointing
Safe dedupe actions (verification before deletion, hard links vs. reflinks, metadata/ACLs)

Assume a cross-platform target (Linux/macOS/Windows) unless noted otherwise. Include implementation-oriented guidance (APIs, flags, data structures) where helpful.

Identify and mitigate deduplication program risks

Quick Overview

System Design: Robust File Deduplication in the Real World

Context

Prompt

Solution

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