What is PromQL in Prometheus?
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Quick Answer
PromQL is Prometheus query language for selecting and aggregating time-series data — filtering by labels, applying functions like rate() and histogram_quantile(), and computing aggregations for dashboards and alerts.
Detailed Answer
It operates on instant and range vectors: for example rate(http_requests_total[5m]) gives per-second request rate, and sum by (service) aggregates across instances. PromQL powers both Grafana panels and alerting rules. Understanding rate/increase on counters and quantiles on histograms is the practical core.
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Interview Tip
Show a real snippet like rate(http_requests_total[5m]) — demonstrating you can actually write PromQL beats defining it.
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