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Google·Software Engineer·Onsite - System Design / Architecture·Staff

StaffPrefer not to say
Jul 2026

Summary

Google engineering manager interview with a single system design question that sounds like a joke until you realize they're completely serious about it.

Questions Asked (1)

Q1

Design a system to upgrade the software on hundreds of thousands of machines located on the Moon.

System DesignTechnical Trade-offsAdaptability & Ambiguity
Author's notes

My first reaction was to laugh, which was probably not ideal.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, such as bandwidth, latency, and update frequency, then propose a staged rollout architecture with a central control plane and distributed agents on each machine. Emphasize fault tolerance, rollback strategies, and efficient data transfer given the extreme environment.

Pro tip: Highlight the importance of designing for partial failures and network partitions, as the Moon's communication links are unreliable and high-latency. Also, consider using a peer-to-peer or gossip protocol to reduce Earth-Moon bandwidth usage.

1. Clarify Requirements and Constraints

Ask questions to understand the scale, update size, frequency, acceptable downtime, and communication infrastructure between Earth and Moon. Identify constraints like bandwidth, latency, and power availability.

2. High-Level Architecture

Propose a central update service on Earth that distributes updates to a set of relay nodes on the Moon, which then propagate to machines via a hierarchical or peer-to-peer network. Include a lightweight agent on each machine to manage downloads and installations.

3. Update Distribution Strategy

Design a mechanism to efficiently transfer large updates over limited bandwidth, such as delta encoding, compression, and multicast or gossip protocols. Consider scheduling updates during low-usage periods to minimize impact.

4. Rollout and Rollback

Implement a phased rollout with canary deployments to detect issues early. Ensure atomic updates with rollback capability in case of failures, and maintain version compatibility across the fleet.

5. Monitoring and Recovery

Set up telemetry to monitor update progress and machine health. Design for automatic retries and self-healing, and include manual intervention points for critical failures.

Key Points to Mention

  • Bandwidth optimization techniques like delta updates and compression
  • Fault tolerance and resilience to network partitions
  • Phased rollout with canary testing and rollback
  • Peer-to-peer or gossip protocols for efficient distribution
  • Atomicity and consistency of updates across machines
  • Monitoring and telemetry for remote diagnostics

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