Estimation question

Estimate how much data YouTube delivers every day.

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

Estimation skill through clean decomposition of a large-scale infrastructure number, not the precise data figure.

Restate the question: total daily data delivered globally through video streaming, combining views and average file size.
Estimate daily video views or watch hours, stating an assumption for total daily watch time across the user base.
Estimate average bitrate or data consumption per hour of video, distinguishing standard versus high-definition streaming as a weighted assumption.
Multiply watch hours by average data per hour to reach a daily total, showing the arithmetic clearly.
Sanity check the result against general awareness of internet traffic being dominated by video, adjusting if the number seems implausible.
State a final illustrative range and flag that the split between mobile and desktop or resolution mix is the biggest source of uncertainty.

Breaks the calculation into watch hours and per-hour data consumption explicitly, rather than guessing one combined number.
States a clear resolution mix assumption, for example a blended average between standard and high-definition streaming, since this drives most of the variance.
Shows the full multiplication chain so the reasoning can be audited step by step.
Sanity checks against a general awareness that video dominates global internet traffic, adjusting the estimate if it seems too low or high relative to that scale.

Guessing a single large number with no decomposition into watch hours and per-hour data usage.
Ignoring the resolution mix, which is the single biggest driver of the final estimate.
Not sanity checking the result against any real-world reference point.

How would your estimate change if mobile viewing, which uses more data-efficient compression, dominated the mix?
What's the biggest lever that could change this number by an order of magnitude?