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DevOps & Automation · Advanced

Cardinality

In observability, the number of unique time series created by the combinations of metric label values.

Definition

Adding labels with many unique values, such as user IDs or request IDs, can explode series count and overwhelm a metrics database. High-cardinality data belongs in logs or traces instead.

Example

Labeling http_requests_total with customer_id for a million customers creates a million series per status code.

Exam tip

High-cardinality labels are a classic Prometheus performance anti-pattern.

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