Back-of-the-envelope estimation.

also: back of the envelope estimation · back-of-envelope estimation · back-of-the-envelope · capacity estimation

Quick, rounded arithmetic on traffic, storage, bandwidth and servers, so design decisions rest on numbers instead of guesses.

the two-minute refresher

Four estimates: traffic (requests/s), storage, bandwidth and infrastructure (servers).
Daily actions = DAU × actions per user; RPS ≈ daily actions ÷ 86,400 (about ÷ 100,000).
Size for the peak, not the average, often 2-3× the average or more.
Round aggressively and say your assumptions out loud: the reasoning matters more than the digits.

also: back of the envelope estimation · back-of-envelope estimation · back-of-the-envelope · capacity estimation

Quick, rounded arithmetic on traffic, storage, bandwidth and servers, so design decisions rest on numbers instead of guesses.

Four estimates: traffic (requests/s), storage, bandwidth and infrastructure (servers).
Daily actions = DAU × actions per user; RPS ≈ daily actions ÷ 86,400 (about ÷ 100,000).
Size for the peak, not the average, often 2-3× the average or more.
Round aggressively and say your assumptions out loud: the reasoning matters more than the digits.