Prometheus & Observability
Metrics, PromQL and alerting explained from first principles. Learn how Prometheus scrapes, stores and queries time series — and remember it with spaced repetition.
- practice cards
- 73
- practice cards
- per day
- ~10 min
- per day
- level
- Beginner → Intermediate
- level
- modules
- 5
- modules
What is Prometheus?
Prometheus is an open-source monitoring system built around a pull model: it scrapes numeric metrics from instrumented targets over HTTP and stores them as time series, each identified by a metric name and a set of labels.
On top of that data sits PromQL, a query language for slicing, aggregating and computing rates over those series — the engine behind dashboards, recording rules and alerts. Knowing the difference between a counter and a gauge, or rate() and irate(), is what separates dashboards that lie from dashboards you can trust.
This track covers the whole loop — exposition format and exporters, the four metric types, PromQL, and alerting through Alertmanager — and uses spaced repetition so the concepts stick when you are on call and need them most.
5 modules, seed to bloom
Each module is a set of practice cards — 73 in total. Answer, review, and watch your knowledge grow from seed to full bloom.
Observability Concepts
Metrics, logs and traces, golden signals, SLI/SLO/SLA, and the pull model
12 cardsPrometheus Fundamentals
Architecture, the TSDB, scraping and service discovery, metric types, and exposition
15 cardsPromQL
Vectors and selectors, rate functions, aggregation, histogram_quantile, and operators
20 cardsInstrumentation & Exporters
Client libraries, exporters, the Pushgateway, naming conventions, and label practices
12 cardsAlerting & Dashboarding
Alerting and recording rules, the for clause, Alertmanager routing, and dashboard queries
14 cardsSample questions
A taste of the real cards. Pick an answer, then reveal the explanation.
What is the core component of the Prometheus architecture?
- AThe Prometheus server that scrapes and stores samples
- BThe Alertmanager that routes and dispatches the alerts
- CThe Pushgateway that buffers short-lived batch jobs
- DThe node_exporter that exposes host-level metrics
What does an instant vector contain in PromQL?
- AOne sample per series at a single point in time
- BA range of samples per series over a time window
- CA single scalar number with no associated series
- DA string literal value used inside a label match
What is the purpose of a Prometheus client library?
- ATo instrument app code and expose its own metrics
- BTo scrape the remote targets and store their samples
- CTo route fired alerts to the correct receivers
- DTo render dashboards from stored time series
What does an alerting rule define in Prometheus?
- AA PromQL condition that triggers an alert when true
- BA precomputed query saved as a brand new time series
- CA routing tree that maps alerts onto receivers
- DA scrape job describing which targets to collect
Learn it once, keep it for good
Answer a question
Each card is one practical concept with multiple options. Pick what you think is right.
Get the full answer
See the correct option plus a clear explanation, and a link to deeper docs when one is available.
Review at the right time
A spaced-repetition engine (SM-2 or FSRS) resurfaces each card just before you would forget it.
Why Prometheus is worth your time
The de-facto cloud-native monitoring stack
Prometheus is the metrics backbone of Kubernetes and most modern infra. Fluency here is a core SRE skill.
Query data with confidence
Understanding PromQL and metric types means your alerts fire on real problems, not noise.
Instrument the right way
Knowing counters, gauges, histograms and summaries lets you expose metrics that actually answer questions.
Interview-ready
PromQL, the pull model and alerting design are staple observability and SRE interview topics.
Common questions
Do I need monitoring experience? +
No. The track starts from the pull model and metric types, so beginners and engineers formalizing what they already half-know both benefit.
Does it cover PromQL? +
Yes — PromQL is the largest module, covering instant vs range vectors, rate/increase, aggregation, histograms and common pitfalls.
Is it free? +
Yes, completely free. No registration or credit card is required, and all your progress is stored locally in your browser.
Will this prepare me for the PCA exam? +
It is not an exam dump, but it covers the conceptual core the Prometheus Certified Associate tests, and pairs well with hands-on practice.
Ready to master Prometheus?
Plant your first seed today. Ten minutes a day is all it takes to turn metrics into monitoring you can trust.