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

Senior
May 2026

Summary

Google PM interview with a classic Fermi-style estimation question. Pretty short experience to report but the question itself was a trip.

Questions Asked (1)

Q1

Estimate the bandwidth in bits per second of a Boeing 747 flying across the Atlantic Ocean with its cargo hold filled with CD-ROMs.

Product Analytics & MetricsTechnical Trade-offs
Author's notes

I stared at this for a second because it sounds like a joke but they were completely serious.

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AI HintsAI Generated

Suggested Approach

Break the problem into two parts: the total data volume (number of CDs × capacity per CD) and the total transit time (flight duration). Then divide data by time to get bandwidth, stating assumptions clearly and sanity-checking the result against familiar network speeds.

Pro tip: Frame the answer around the trade-off between latency and bandwidth: the 747 has enormous bandwidth but terrible latency, which is why it's a classic example of why bandwidth alone doesn't determine user experience.

1. Estimate data volume

Assume a 747 cargo hold can carry about 100 tons of CDs. Each CD weighs roughly 15 grams and holds about 700 MB, so calculate total capacity in bits.

2. Estimate transit time

A transatlantic flight takes about 8 hours, including loading and unloading. Convert this to seconds for the bandwidth calculation.

3. Compute bandwidth

Divide total bits by total seconds to get bits per second. Simplify the arithmetic to get a rough order of magnitude.

4. Sanity-check and contextualize

Compare the result to typical network speeds (e.g., 1 Gbps) and discuss the latency implications. Mention that the effective bandwidth for interactive use is much lower due to the 8-hour delay.

Key Points to Mention

  • Assumptions about CD capacity (700 MB) and weight (15 g)
  • Cargo capacity of a 747 (approx. 100 tons)
  • Flight time (approx. 8 hours) and conversion to seconds
  • Calculation: total bits / total seconds
  • Comparison to common network speeds (e.g., 1 Gbps)
  • Latency vs. bandwidth trade-off and implications for product design

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