Monitoring & Observability

The Three Pillars

Metrics, logs, and traces and what each is good for.

25 min read beginner 3 objectives

Status

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What you will learn

  • Distinguish the three signals
  • Pick the right signal
  • Understand observability vs monitoring

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The basics, in plain English

Once your software is running, you need to know if it is healthy. Observability means being able to understand what is happening inside your system from the outside. It usually rests on three pillars: metrics, logs, and traces, which together answer what is wrong, why, and where.

Monitoring
Watching your system to spot problems, ideally before users do.
Observability
Being able to understand the inside of your system from the signals it gives off.
Metrics
Numbers measured over time, like CPU usage or requests per second.
Logs
Text records of events, like a diary your software writes as it runs.
Traces
A timeline showing how one request traveled through all your services.
Why it matters
You cannot fix what you cannot see, so these signals guide every fix.
01

Signals

Metrics are cheap aggregates over time, logs are detailed events, traces follow a request across services. Together they make a system observable.

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