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Anthropic·Software Engineer·Onsite - Coding / Algorithms·Intermediate

Intermediate
Jun 2026

Summary

Onsite coding round at Anthropic for a software engineer role. The interviewer was completely stone-faced the whole time, barely said a word, and every response I got was just a flat 'ok, good' with zero indication of whether I was on the right track.

Questions Asked (1)

Q1

Design and implement a file system (object-oriented / class-based approach).

System DesignAlgorithms & Data StructuresTechnical Trade-offs
Author's notes

The silence from the interviewer made this so much harder than it needed to be.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and scope (e.g., in-memory vs. persistent, concurrency, permissions), then design a class hierarchy with core entities like File, Directory, and FileSystem. Implement key operations (create, read, write, delete, list) and discuss trade-offs such as using a tree structure, handling paths, and ensuring thread safety.

Pro tip: Demonstrate awareness of real-world constraints by mentioning how you'd handle edge cases like circular symlinks, concurrent access, and efficient directory listing; this shows maturity beyond basic CRUD.

1. Clarify Requirements

Ask questions to define scope: in-memory or persistent? Single-threaded or concurrent? What operations are needed (create, read, write, delete, move, copy)? Any permissions or metadata?

2. Design Class Hierarchy

Define core classes: FileSystem, Directory, File, and possibly Symlink. Use inheritance or composition (e.g., File and Directory inherit from a common Node). Include attributes like name, size, timestamps, and parent references.

3. Implement Core Operations

Implement methods for creating, reading, writing, deleting, and listing. For directories, use a map for children to allow O(1) lookup. Handle path resolution (absolute vs. relative) and traversal.

4. Address Edge Cases and Concurrency

Discuss handling of duplicate names, circular references, and permissions. If concurrent, propose locking strategies (e.g., per-node locks or read-write locks) to ensure thread safety.

5. Discuss Trade-offs and Extensions

Compare design choices: tree vs. flat structure, in-memory vs. on-disk, eager vs. lazy loading. Mention potential extensions like journaling, quotas, or caching.

Key Points to Mention

  • Use of composite pattern for uniform treatment of files and directories
  • Path resolution and normalization (handling '.', '..', absolute vs. relative paths)
  • Efficient directory listing with hash maps for O(1) child lookup
  • Concurrency control: locks, atomic operations, and avoiding deadlocks
  • Memory management: lazy loading, caching, and eviction policies
  • Trade-offs between simplicity and features (e.g., permissions, symlinks)

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.