Observability: Logs, Metrics & Traces

What observability actually is, how logs, metrics, and traces each see a different slice of your running system, and how to use all three together to find out why something is slow.

1. Monitoring vs Observability Monitoring watches the known things you already set up alerts for; observability is being able to ask brand-new questions about why a system is misbehaving, without shipping new code to answer them.
2. The Three Pillars Logs are discrete events, metrics are numbers aggregated over time (counters, gauges, histograms), and traces follow one request across services as a tree of spans - each sees something the others can't.
3. Putting Them Together Debug a real slowdown end to end - a metric alert points at the symptom, a trace finds the slow service, logs explain why - plus a quick map of the tool landscape and the two traps that bite teams: cardinality explosions and alert fatigue.