Generate PromQL queries for calculating error rates, aggregating metrics across labels, creating histogram percentiles, writing recording rules, and building SLO burn-rate alerts following Prometheus best practices. Use when creating new PromQL queries, implementing monitoring and alerting rules, building observability dashboards, working with Prometheus metrics (counters, gauges, histograms, summaries), or applying RED (Rate, Errors, Duration) and USE (Utilization, Saturation, Errors) monitoring patterns.