THE SPAN ATTRIBUTE THAT BLEW UP YOUR OBSERVABILITY BILL

Summary from the TLDR Data newsletter

A high-cardinality span attribute can quietly multiply metric series even when trace volume and sampling remain flat. Sampling reduces stored trace bytes, not the distinct label combinations produced upstream by span metrics. Keep identifiers on traces, bucket them before metrics aggregation, and set cardinality and expiration limits so one deployment cannot turn a temporary dimension into a lasting observability bill.