Anthropic·Software Engineer·Onsite - System Design / Architecture·Senior

SeniorPrefer not to say

Jun 2026

Summary

System design round at Anthropic for a hardware engineer role. The question was a distributed systems problem which felt a bit out of left field for the role, but I guess they want to know you can think through infrastructure problems end to end.

Questions Asked (1)

Design a peer-to-peer file distribution system that takes a 10GB file from a single bandwidth-limited source and propagates it to thousands of interconnected hosts, each with constrained upload and download capacity, until every node has the full file.

System DesignTechnical Trade-offs

Author's notes

Spent the first few minutes just thinking about the naive approach where the source pushes to each host sequentially, which obviously falls apart at scale.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints (file size, number of peers, bandwidth limits, churn). Then propose a peer-to-peer protocol like BitTorrent with chunking, swarming, and tit-for-tat incentives, and discuss trade-offs around scalability, fairness, and reliability.

Pro tip: Emphasize that the source's upload bandwidth is the bottleneck, so the design should minimize reliance on it by enabling peers to exchange chunks directly and using a rarest-first strategy to maximize availability.

1. Clarify Requirements and Constraints

Ask about file size, number of peers, bandwidth asymmetry, churn rate, and whether security or incentives are needed. Confirm that the goal is to distribute the file to all peers as efficiently as possible.

2. High-Level Architecture

Propose a peer-to-peer network where the source seeds the file and peers exchange chunks. Consider a tracker or DHT for peer discovery and a swarm for data exchange.

3. Chunking and Swarming

Divide the file into fixed-size chunks (e.g., 256KB-1MB) and use a rarest-first chunk selection policy to ensure even distribution. Peers download chunks from multiple sources in parallel.

4. Incentives and Fairness

Implement tit-for-tat to encourage uploads: peers prioritize sending to those who upload to them. Consider optimistic unchoking to bootstrap new peers.

5. Scalability and Reliability

Discuss how the design scales with thousands of peers, handles churn, and ensures data integrity via checksums. Mention potential bottlenecks and mitigation strategies.

Key Points to Mention

BitTorrent-like protocol with tracker/DHT for peer discovery
File chunking and rarest-first chunk selection
Tit-for-tat incentive mechanism to prevent free-riding
Parallel downloading from multiple peers to utilize bandwidth
Handling peer churn and data integrity with checksums
Trade-offs: overhead of coordination vs. efficiency, fairness vs. speed

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