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Estimationstretch
How many messages per second does a large messaging app handle at peak?
How to approach it
Go from daily active users to messages per day, then convert to an average per second and multiply by a peak factor.
How a strong answer opens
“I'll go from daily active users to messages per day, convert to an average per second, then apply a peak factor, because the peak, not the average, decides capacity.”
Outline of a strong answer
Try answering out loud for a few minutes before you open this.
- Assume daily active users as a round number
- Messages sent per user per day
- Messages per day
- Divide by 86,400 seconds
- Apply a peak-to-average factor, such as 2 to 3 times, for evening or holiday spikes
- Explain why the peak, not the average, decides server capacity
Where this question usually goes wrong
Stopping at the daily average per second, or making a unit error when converting days to seconds.
Learn the method
Worked cases 5 to 8 in Module 3, Estimation.
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