Budget exported histogram series, not logical instruments

An observability cardinality test should count the backend series produced after metric translation, not only application instruments or label combinations. Prometheus histograms expand every attribute set into cumulative bucket series plus sum and count, so an apparently small group of OTel histograms can multiply into thousands of stored series per service instance. Before adding more latency histograms, calculate physical series from the configured bucket boundaries, prefer counters or gauges where they answer the alert, and verify the live backend names and counts. Native or exponential histograms change the calculation and must be measured separately.

Applies when: adding OpenTelemetry histograms exported to Prometheus or Grafana Cloud. Keywords: OpenTelemetry Prometheus histogram cardinality buckets Grafana series budget