Design one system end to end
By the end of today you can take a design question from requirements to a defended architecture in under an hour, and hold your position under sustained challenge.
YesterdayDays 57 to 65 covered method, estimation, scaling, caching, replication, consistency, queues, real-time and service boundaries.
TomorrowTomorrow begins AI Engineering, where a model becomes one more component in the systems you now understand.
Why this matters
This is the interview, and more importantly it is the meeting where a real system gets decided. Being able to reason out loud under challenge is the whole skill.
- Designing under challenge
- Finding the bottleneck
- Tradeoff reasoning
- The design method
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.
5 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
55 minWrite up the video platform design as you would hand it to a colleague: requirements, estimates with assumptions, API surface, data model, architecture diagram in text, and a section for each of the six challenges with your answer. Then write the strongest objection to your own design and answer it.
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
Free · sign inRate yourself against five named criteria per concept. Completion and mastery are tracked separately, and anything you rate shakily comes back automatically on a spaced schedule.
Recap
- 01Requirements, then numbers, then the simplest design, then the bottleneck
- 02Every cache needs a key, a TTL and an invalidation trigger
- 03Deleting data everywhere is hard because copies live where you cannot reach
- 04Knowing which part would frighten you at 3am is part of the design
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.