What is observability?
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Quick Answer
Observability is the ability to understand a system internal state from its external outputs — the three pillars being metrics, logs, and traces — so you can ask new questions about behavior without shipping new code.
Detailed Answer
Monitoring tells you whether known failure modes are happening; observability lets you investigate unknown ones. Metrics quantify trends, logs give event detail, and distributed traces follow a request across services. Strong observability shortens MTTR by making root cause discoverable rather than guessed.
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Interview Tip
Distinguish observability (explore unknown-unknowns) from monitoring (watch known conditions) — that nuance is what separates senior answers.
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