Rookie Mistakes in Prometheus Recording Rules

Five rookie mistakes in recording rules and how they show up. Each costs cardinality, performance, or signal.

Recursive rules

Rule A computes from rule B; rule B computes from rule A. The evaluation engine handles it; the result is stale.

Avoid. Compose rules in a DAG with explicit ordering.

Over-using rules

Every dashboard query becomes a rule. Cardinality explodes; storage suffers.

Rules are for queries used by many dashboards. Single-use queries do not need pre-computation.

Under-using rules

Heavy queries that run on every dashboard load. Slow rendering; high CPU on the storage.

If a query is run >100 times/day and takes >1s, recording rule it.