Scaling up, scaling out, and load balancing
By the end of today you can say when a bigger machine beats more machines, explain what statelessness actually requires, and name the problems that only appear once there is more than one server.
YesterdayOn Day 58 you calculated whether one machine is enough. Today assumes it is not.
TomorrowTomorrow, caching, which is usually the cheaper answer to the same pressure.
Why this matters
Horizontal scaling is treated as the obvious answer and it introduces an entire category of problem that did not exist before. Knowing which problems those are is the point of today.
- Scaling up or out
- Statelessness
- Load balancing
- Problems that need two machines
Learn it
80 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.
4 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
50 minRun two instances of your containerised API behind a simple load balancer. Confirm requests reach both. Then deliberately break statelessness by storing something in memory on one instance, and observe the inconsistent behaviour. Move that state to a shared store and confirm it is fixed.
Recall it
20 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
- 01Vertical scaling adds no new failure modes, which is worth a great deal
- 02Horizontal scaling requires statelessness before anything else
- 03A health check that lies takes down a healthy fleet
- 04Several servers create problems that one server never had
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.