The Cardinality Budget Per Service

Cardinality is the single biggest cost driver in metrics platforms. The budget pattern, the audit, and the team behaviour it changes.

Set the budget

10,000 unique time series per service per metric. Above that requires explicit approval.

The number is policy. Pick one that lets the team move fast but caps cost growth.

Audit weekly

Top 10 highest-cardinality metrics per service. Sorted by series count.

Above-budget metrics get a fix-by date. Either cap the cardinality or convert to logs.

When to convert

If the metric needs a label that has high cardinality (user_id, request_id), it should probably be a log.

Logs handle high cardinality natively; metrics do not. Use the right tool.