Observability: logs, metrics, and traces
By the end of today you can say which of the three signals answers which kind of question, choose what to alert on, and explain why a dashboard full of green graphs can coexist with users unable to log in.
YesterdayOn Day 49 you added logs. Today you learn what logs cannot answer and what the other two signals are for.
TomorrowTomorrow you use these signals to find where time is actually going.
Why this matters
Monitoring tells you something is wrong. Observability lets you ask why without shipping new code. The gap between them is where long outages live.
- Logs, metrics and traces
- Metrics and percentiles
- Tracing
- Alerting on symptoms
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
45 minAdd three metrics to your API: a request counter by endpoint and status, a latency histogram, and one business counter such as successful logins. Then write down two alerts you would set, phrased as things a user would notice, and explain what each would NOT catch.
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
- 01Logs explain one case; metrics show trends; traces show where time went
- 02Averages hide the tail, and the tail is who complains
- 03Alert on what users feel, not on what machines report
- 04Green dashboards often mean you measured the easy things
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.