X_METRIC_CARDINALITY

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

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

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