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

Intermediate
Jun 2026

Summary

Google PM interview with a classic estimation question about campus internet bandwidth. Pretty standard fermi-style problem but I underestimated how much structure they wanted around the assumptions.

Questions Asked (1)

Q1

Estimate the total internet bandwidth needed to support a campus of 1000 graduate students.

System DesignProduct Analytics & MetricsAdaptability & Ambiguity
Author's notes

I jumped straight into numbers without setting up my assumptions clearly, which I think hurt me.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the scope: what types of internet usage are we estimating (academic, streaming, gaming, etc.) and during what time period (peak vs. average). Then break down usage into categories, estimate per-student bandwidth for each, and aggregate to get total bandwidth, considering peak concurrency and overhead.

Pro tip: Always state your assumptions explicitly and sanity-check the final number against real-world benchmarks (e.g., typical campus network speeds). This shows you can handle ambiguity and validate your estimates.

1. Clarify scope and assumptions

Ask clarifying questions to define what 'internet bandwidth' means (e.g., peak vs. average, wired vs. wireless, internal vs. external traffic) and the usage profile of graduate students.

2. Categorize usage types

Break down internet usage into common categories such as academic research, video streaming, video conferencing, cloud services, social media, and gaming.

3. Estimate per-student bandwidth per category

For each category, estimate the bandwidth required per student (e.g., HD video streaming ~5 Mbps, video conferencing ~2 Mbps) and the likelihood of simultaneous use.

4. Calculate aggregate and peak bandwidth

Sum the per-student bandwidth across categories, then multiply by the number of students and apply a concurrency factor to estimate peak total bandwidth.

5. Sanity-check and adjust

Compare the estimate to typical campus network capacities (e.g., 1-10 Gbps) and adjust for overhead, future growth, and redundancy.

Key Points to Mention

  • Peak vs. average bandwidth and concurrency factor
  • Typical bandwidth requirements for common applications (streaming, video conferencing, etc.)
  • Assumptions about student behavior and usage patterns
  • Overhead for protocols, retransmissions, and network inefficiencies
  • Scalability and future-proofing (e.g., increasing demand over time)
  • Comparison to real-world campus network benchmarks

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