May 14, 202611 min readObservability

Time-Series Cardinality Budgeting for Prometheus

A governance model for labels and metric families that keeps Prometheus fast during incidents while preserving useful debugging signals.

Cardinality blowups are predictable if you do not enforce label budgets.

Budget by Metric Family

Assign a max active-series target for each service and block merges that exceed policy.

metric_relabel_configs:
  - source_labels: [path]
    regex: "/users/[0-9]+"
    target_label: path
    replacement: "/users/:id"

Metrics should summarize systems, not mirror event logs.