Prometheus is an open-source monitoring system and time series database originally built at SoundCloud, now a graduated CNCF project, widely used for collecting numeric metrics and powering alerting in cloud-native environments.
The site offers the latest release downloads, a thorough documentation set covering the data model, PromQL query language, alerting rules, and service discovery, plus a large ecosystem of exporters and client libraries.
It suits site reliability and platform engineers who need to scrape metrics from services, write alerting rules, and build dashboards; it also helps developers instrument applications with the official client libraries.
Compared with Graphite it stores multidimensional labels natively, and compared with commercial APM suites it is self-hosted and flexible, though long-term storage and global view often require Thanos or Cortex alongside.
Secure exposed instances with authentication and network controls, avoid scraping high-cardinality metrics that blow up memory, and keep retention and rule evaluation tuned to your cluster size.