Anatomy of a backend
By the end of today you can open an unfamiliar backend and name each layer, say what belongs in each, and explain what goes wrong when business logic ends up inside a route handler.
YesterdayOn Day 34 you traced a request into a server and stopped at the boundary. Today you go inside.
TomorrowTomorrow you build one, so the layers stop being a diagram and become code you wrote.
Why this matters
Every backend you meet is some version of the same layering. Recognising it means you can find anything in an unfamiliar codebase in minutes rather than hours.
- Backend layers
- Routing
- The service layer
- Layer responsibility
Learn it
75 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
40 minFind a small open-source Python or Node backend on GitHub. Without reading everything, locate the routes, pick one endpoint, and trace it down through every layer, writing what each layer does. Then name one place where a responsibility has leaked into the wrong layer.
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 server is a loop that maps requests to functions
- 02Each layer should be ignorant of the ones above it
- 03Logic inside a route handler cannot be tested or reused
- 04Layering costs indirection, and only pays when the logic is real
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.