Estimating traffic, storage, and capacity
By the end of today you can turn a vague requirement into numbers in a couple of minutes, and use those numbers to decide whether a design needs anything beyond one server.
YesterdayOn Day 57 you learned to establish requirements before choosing anything. Today you turn those requirements into numbers.
TomorrowTomorrow you find out what to do when the numbers genuinely exceed one machine.
Why this matters
Estimation is what separates a design from a wish. It also settles arguments: many proposed complexities dissolve once you calculate that the load fits comfortably on one machine.
- Capacity estimation
- Back-of-envelope arithmetic
- Read-write ratio
- Peak against average
Learn it
70 minCopy this into Claude or ChatGPT. It quizzes you before it explains anything, which is deliberate. The resources under it are how you check what it told you.
Today's Master Prompt
Free · sign inA prompt written for this day alone: your level, the exact scope, what to leave out, and an instruction to quiz you before it explains anything. Paste it into Claude or ChatGPT and it teaches you today's material.
Check it against something that is not a model
An assistant can be fluent and wrong, and on a topic you met today you will not catch it. These cover the same ground and were made by people who do this for a living, so they are what you hold the explanation up against. They are other people's work and we only link to them, so judge them for yourself.
3 hand-picked resources
Free · sign inVideos, official docs and articles covering the same ground, each opened and annotated by hand. They are what you check the assistant against on a day you cannot yet catch it being wrong.
Build it
45 minEstimate for a photo sharing service with 100,000 daily users: requests per second at average and peak, storage per year assuming two uploads per user per day at 2MB each, and the read-to-write ratio. Then write one paragraph on what those numbers mean for the architecture, including what you would NOT build.
Recall it
25 minAnswer out loud, reveal, then mark honestly whether you had it. That score is the only thing on this page you do not get to choose.
5 recall questions
Free · sign inQuestions you answer from memory, then grade yourself against the real answer. The score is carried into the mastery rating below it, so an honest miss cannot quietly become a tick.
Rate it
Completion and mastery are tracked separately. Be honest, because an inflated rating only means the concept resurfaces sooner.
Mastery tracking
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Recap
- 01A million a day is about twelve a second, which is nothing
- 02Peak is two to five times average, and peak is what you design for
- 03The read-write ratio decides most of the architecture
- 04Most systems people want to distribute fit on one machine
Your progress
Free · sign inMark days complete, pick up where you left off across devices, and watch completion and mastery diverge. Free, and the account exists only so ninety days of work cannot vanish with a cleared browser.