Estimation question

How would you design a service like Instagram? Estimate server and storage requirement for peak traffic.

Practice this question out loud. An AI interviewer asks it, follows up like a real interviewer would, and scores your answer. Type or speak.

What this question tests

Technical estimation combining product scoping with back of envelope infrastructure sizing.

Scope the service: photo and short video sharing at Instagram's scale, focusing on storage and peak read bandwidth.
Estimate daily uploads: assume 500 million daily active users, with 5 percent uploading one photo daily, giving 25 million photos per day.
Estimate storage per photo: assume 2MB average with multiple resolutions stored, roughly 5MB effective per photo including thumbnails.
Calculate daily storage growth: 25 million times 5MB gives roughly 125TB added per day.
Estimate peak read traffic: assume each photo is viewed 100 times on average, spread over a peak factor of 3x average load.
Size servers using a rough requests per second budget, then state the estimate as an order of magnitude range, not a precise figure.

Breaks the problem into storage and bandwidth separately, since they require different infrastructure reasoning.
States each assumption explicitly, DAU, upload rate, and file size, so the math is auditable step by step.
Gives a clean final number with units, roughly 125TB per day of new storage, rather than an ambiguous figure.
Accounts for peak versus average load using a stated peak factor, showing awareness of real traffic patterns.

Giving a final number with no visible breakdown of storage versus bandwidth reasoning.
Ignoring multiple resolution storage (thumbnails, compressed versions), which significantly changes real storage needs.
Not distinguishing peak load from average load when sizing servers.

Chapters of the AI PM course that teach what this question tests.