Tips for estimating
Play this lessonThis lesson comes with a live-code challenge and a chapter quiz.Estimation is about the process, not a perfect answer. Interviewers want to see how you think.
- Rounding and approximation. Don't compute 99,987 / 9.1 exactly. Round it to 100,000 / 10 = 10,000. Precision isn't the point.
- Write down your assumptions so you (and the interviewer) can refer back to them.
- Label your units. Is "5" five KB or five MB? Write
5 MBto avoid confusion. - Practice the common ones: QPS, peak QPS, storage, cache size, number of servers.
Handy shortcut: a day has 86,400 seconds, roughly 100,000 (10⁵). So "X per day" ÷ 10⁵ ≈ "per second". For example, 100 million per day ≈ 1,000 per second.
Key takeaways
- Round aggressively, write assumptions, label units.
- 1 day ≈ 10⁵ seconds.