Latency, throughput, and profiling intuition
By the end of today you can tell latency and throughput apart, estimate roughly what an operation should cost before measuring, and find where time actually goes rather than where you assumed.
YesterdayOn Day 53 you learned to see what a system is doing. Today you interpret what you see and act on it.
TomorrowTomorrow, what to do about the failures that come from things simply being slow or unavailable.
Why this matters
Almost all performance work by inexperienced engineers is spent optimising things that were never slow. Knowing the rough cost of common operations tells you where to even look.
- Latency and throughput
- Latency orders of magnitude
- Profiling
- Finding the bottleneck
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.
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
50 minTake your slowest endpoint. Before measuring, write down where you think the time goes and roughly how much, using the latency table. Then profile it and compare against your prediction. Fix the single largest cost, measure again, and record the improvement.
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
- 01Latency is one operation; throughput is how many per second, and they can conflict
- 02The latency table tells you where the time is before you profile
- 03CPU-bound, I/O-bound and contended have completely different fixes
- 04Optimising five percent of the time buys you at most five percent
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.