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

Senior
May 2026

Summary

PM interview at Google with a classic estimation question about Google Photos storage. Pretty straightforward product sense exercise but the scale of it made me second-guess my numbers the whole way through.

Questions Asked (1)

Q1

Estimate how many photos are uploaded to Google Photos annually and how much total storage that would require.

Product Analytics & MetricsSystem DesignProduct Sense & Ideation
Author's notes

I started with global smartphone users and tried to work down to active Google Photos users, then estimated photos per user per day.

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AI HintsAI Generated

Suggested Approach

Break the problem into two parts: first estimate the number of photos uploaded annually by segmenting users and estimating upload frequency, then estimate storage by multiplying by average file size. Use a top-down approach with clear assumptions, and validate with sanity checks.

Pro tip: State your assumptions explicitly and round numbers to simplify calculations; this shows structured thinking and makes your answer easy to follow. Also, consider mentioning that Google Photos offers free unlimited storage for compressed photos, which affects storage estimates.

1. Clarify scope and assumptions

Define what 'photos' includes (e.g., images, videos) and the time frame (annual). Assume global Google Photos users and average upload behavior.

2. Estimate user base

Start with world population, internet users, smartphone users, and Google Photos adoption rate to estimate monthly active users.

3. Estimate upload frequency

Segment users by activity level (e.g., heavy, medium, light) and assign average photos uploaded per user per year.

4. Calculate total photos uploaded annually

Multiply the number of users in each segment by their upload frequency and sum to get total annual uploads.

5. Estimate storage per photo and total storage

Assume average file size per photo (e.g., 3 MB for compressed, 5 MB for original) and multiply by total photos to get total storage in bytes, then convert to petabytes/exabytes.

Key Points to Mention

  • Segmentation of users by activity level (heavy, medium, light uploaders)
  • Average file size per photo (consider compression and video uploads)
  • Google Photos' free unlimited storage for compressed photos vs. original quality
  • Growth trends in photo uploads due to increasing smartphone usage
  • Sanity check: compare estimate to known Google Photos user base and storage capacity
  • Conversion of bytes to larger units (GB, TB, PB, EB) for clarity

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