Interview LineLesson
Back-of-the-envelope: find the number that matters
The requirements are on the board. In about five minutes, turn "2 million daily users" into requests a second, terabytes a year and megabytes a second — with round numbers — and spot the one result that changes the design.
12 minEasyStation: Back-of-the-envelope estimatesMembers lesson
Membership isn’t open yet. The free lessons are open — 19 of them.
- Interview & rubric
- Requirements and scope
- Back-of-the-envelope estimates
- API design
- Data model
What you'll be able to do
- 1Turn daily users and actions per user into average and peak requests a second, a read:write ratio, storage per year and bandwidth, using round numbers and about 100,000 seconds in a day.
- 2Recall the orders of magnitude on the latency ladder — memory, SSD, a round trip inside a data center, a round trip across an ocean — and use them to check whether a latency target is reachable at all.
- 3Choose which estimate changes the design, sanity-check each result against what one machine or one store can handle, and leave fleet sizing to capacity math.
Inside the lesson
- steps
- 11
- questions
- 15
- simulations
- 0