Estimation question

How many queries per second does Gmail get?

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 using known user scale and typical per user activity to derive a systems level throughput number.

Estimate the email product's total active user base, commonly cited around 1.8 billion active users globally.
Estimate the share active on a typical day and average actions per active user per day, checking mail 10 to 15 times, each involving a few queries.
Estimate total daily queries by multiplying daily active users by average queries per user per day.
Convert daily total queries to queries per second by dividing by seconds in a day, accounting for uneven traffic distribution across time zones.
Adjust the estimate upward for peak load, since global usage is not evenly spread across all 24 hours, and state a range for average versus peak.

Anchors on a known, defensible user base figure and builds up through daily actions rather than guessing a queries per second number directly.
Shows the math, 1 billion daily active users times 10 queries a day equals 10 billion queries a day, divided by 86,400 seconds gives roughly 115,000 average queries per second.
Explicitly separates average from peak load, noting real traffic engineering cares more about peak, which could be several times the average.

How would this estimate change during a global event that spikes email traffic?
How would you separate read queries from send or compose queries in this estimate?