How does Prometheus discover what to scrape?
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Quick Answer
Via service discovery (Kubernetes, EC2, Consul, etc.) or static configs, then it pulls /metrics from each target on an interval.
Detailed Answer
Prometheus is pull-based: scrape_configs define jobs with targets from static_configs or service discovery. relabel_configs filter and rewrite target labels before scraping. This model makes targets self-describing and lets Prometheus detect down targets (up == 0).
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Interview Tip
Pull model + relabeling is the architecture answer.
prometheusservice-discoveryscraping