Grafana Skills

---
name: promql
license: Apache-2.0
description: Write, validate, and optimize PromQL for Prometheus / Grafana Mimir / Grafana Cloud Metrics. Covers `rate` vs `irate` vs `increase`, label matchers and regex, `sum / avg / topk / by / without` aggregation, classic + native `histogram_quantile`, ratios with divide-by-zero guards, `absent` / `changes` for staleness, time offsets and `predict_linear`, recording-rule naming, SLO + burn-rate math, and a cardinality-hunting playbook. Use when writing a metric query, fixing wrong p95s, building an error-budget alert, debugging "query is slow", finding the noisy label that blew up cardinality, or migrating a dashboard query to a recording rule — even when the user says "calculate the error rate", "p99 latency", "sum by service", "why is this query slow", or "what's filling Mimir" without naming PromQL.
---

# PromQL Query Patterns

> **Docs**: https://prometheus.io/docs/prometheus/latest/querying/basics/

PromQL returns either an **instant vector**, a **range vector**, or a **scalar**.

**Golden rule:** `rate()` / `increase()` require a range vector ≥ 4× the scrape interval. 60s scrape → use `[5m]` minimum.

## Prerequisites

- A Prometheus / Mimir / Grafana Cloud endpoint to query (`/api/v1/query` or via Grafana Explore)
- The PromQL pattern library in [`references/patterns.md`](references/patterns.md)

## Common Workflows

### 1. Write + validate a query

```bash
# 0. Point at your Prometheus/Mimir. For Grafana Cloud, use the metrics endpoint
#    and add basic auth (-u "<metrics_user>:<token>") to each curl below.
PROM=http://localhost:9090   # or https://prometheus-prod-XX.grafana.net/api/prom

# 1. Sketch the query — for "5xx error rate per service":
EXPR='sum(rate(http_requests_total{status_code=~"5.."}[5m])) by (service)'

# 2. Validate syntax + that the metric/labels exist
curl -sG --data-urlencode "query=${EXPR}" \
  "$PROM/api/v1/query" | jq '.status, (.data.result|length)'
# Expect: "success" and result count > 0. If 0 — check label spelling and scrape activity:
curl -sG --data-urlencode "match[]=http_requests_total" "$PROM/api/v1/series" | jq '.data | length'

# 3. Sanity-check the magnitude — open Grafana Explore, paste the expr,
#    confirm the values look right against a known ground truth (k6 run, log count, etc.)
```

### 2. Common patterns to copy

**Per-status request rate** (aggregate AFTER rate):