~3 sessions a week: read the lesson (~15 min) + run and change its section of obs/demo.py (~25 min). Tick lessons off — progress is saved in this browser.
Why observability, logs, metrics. Lab: add a field to a log line and query it; add a label and watch the series count.
Percentiles, tracing, OpenTelemetry. Lab: move a bucket boundary; add a span and find the new critical path; change the tail-sampling rule.
Prometheus and Grafana, alerting, SLOs. Lab: restart the counter; change the burn-rate thresholds; set a different SLO.
Incident response, root cause, postmortems. Lab: move the detection minute; add a change; write your own postmortem.
Next: the System Design school plans observability into every box, the Scaling school shows what to watch under load, and the School portal has the rest.