Observability (o11y)

Being able to tell what a running system is doing, and why, from the data it emits: logs, metrics and traces.

Monitoring answers questions you planned for: is the server up, is the error rate above a threshold. Observability lets you ask new questions during an incident, such as which customers and which release a slow request belongs to. Logs, metrics and traces are the usual raw material; what matters is whether you can connect them to one request, one user and one deploy. For AI features the same idea is LLM observability.

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Related terms

OpenTelemetry (OTel): An open, vendor-neutral standard and set of SDKs for producing and sending traces, metrics and logs.
SLO and SLI: An SLI is a measured indicator of service quality; an SLO is the internal target for it, stricter than any SLA you sign.
LLM observability: Tracing every model call with inputs, outputs, latency, tokens, cost and the user outcome.
Runbook: A short document that tells someone else how to run a system: where it lives, how to deploy, how to recover.

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