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Google·Product Manager·Onsite - Product Sense / Strategy·Senior

Senior
Jun 2026

Summary

Google PM interview with a classic estimation question about moving a massive amount of data across the country. Pretty technical for a PM role, which threw me off a bit.

Questions Asked (1)

Q1

How long would it take to move 100 petabytes of data from the East Coast to the West Coast?

System DesignTechnical Trade-offsAdaptability & Ambiguity
Author's notes

I started by trying to figure out what method we're even talking about, network transfer vs physical drives on a truck, because the answer is wildly different.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the constraints and assumptions, such as available bandwidth, transfer method (network vs. physical shipping), and whether the data can be compressed or deduplicated. Then, calculate the transfer time using the chosen method, and discuss trade-offs between speed, cost, and reliability. Finally, consider real-world factors like data transfer rates, encryption overhead, and potential bottlenecks.

Pro tip: Acknowledge that for very large datasets, physical shipping (e.g., using AWS Snowmobile or Google Transfer Appliance) is often faster and more cost-effective than network transfer, and mention that Google has its own solutions like Transfer Appliance. This shows you understand practical trade-offs beyond pure math.

1. Clarify Assumptions

Ask clarifying questions to establish key parameters: available bandwidth, whether the data can be compressed, if it's a one-time transfer, and if there are budget or time constraints.

2. Evaluate Transfer Options

Compare network transfer (using dedicated high-speed links) versus physical shipping (using portable storage devices). Consider factors like speed, cost, security, and practicality.

3. Calculate Transfer Time

For network transfer, estimate time based on bandwidth (e.g., 100 Gbps). For physical shipping, estimate based on shipping time plus data loading/unloading. Provide a rough calculation.

4. Discuss Trade-offs and Real-World Factors

Highlight trade-offs: network transfer may be faster but expensive and limited by bandwidth; physical shipping is slower but cost-effective for huge volumes. Mention encryption, data integrity, and potential bottlenecks.

5. Recommend a Solution

Based on assumptions, recommend the best approach, possibly a hybrid, and note that for 100 PB, physical shipping is often optimal. Tie back to product management considerations like cost, time, and reliability.

Key Points to Mention

  • Bandwidth limitations and the difference between theoretical and practical transfer speeds
  • Physical shipping options like AWS Snowmobile or Google Transfer Appliance
  • Data compression and deduplication to reduce transfer volume
  • Cost implications: network egress fees vs. shipping and device costs
  • Security and encryption during transfer
  • Real-world examples: Google's own data transfer methods and past large-scale migrations

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