# X_METRIC_CARDINALITY

## Means

a metric exceeded its series ceiling and is folding into one overflow series

## Typical cause

an unbounded label at the call site — a user id, a path, an email — so every distinct value mints a series and the scrape grows without limit. Past `maxSeries` every further label set folds into one `otel_metric_overflow="true"` series, reported once per instrument rather than once per observation. Also raised at declaration for a `maxSeries` that is not a positive integer

## Fix

drop the unbounded label from the call site, or raise it deliberately: `counter('orders_total', { maxSeries: 4000 })`

[Metrics](/error-codes#metrics)