Estimation question

How would you estimate the space required for Google Photos?

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What this question tests

Estimation of storage infrastructure needs using user count, upload behavior, and file-size assumptions.

Clarify scope: total storage Google must provision globally today for all Google Photos users.
Estimate Photos' active user base, say around 1 billion MAU, based on public Google statements.
Estimate average photos and videos uploaded per user, say 2,000 photos and 50 videos, accounting for varying tenure.
Assume average file sizes, roughly 3MB per compressed photo and 150MB per short video, to compute per-user storage.
Multiply per-user storage by user count, then add overhead for redundancy across data centers, say 2-3x.

Separates photo storage from video storage, since video dominates total bytes despite lower count.
States a replication factor explicitly, since raw need is much smaller than provisioned storage.
Arrives at an order-of-magnitude figure, low hundreds of exabytes, and sanity-checks it against known large-scale cloud storage.

Ignoring video, usually the dominant contributor to total bytes despite being a minority of file count.
Forgetting replication overhead, understating real infrastructure needs.

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