Prometheus

Prometheus is a systems and service monitoring tool, and a Cloud Native Computing Foundation (CNCF) project: it collects metrics from configured targets at regular intervals, evaluates rule expressions against that data, and can trigger alerts when conditions are met.

Its data model is multi-dimensional - time series are identified by a metric name plus a set of key/value labels - and queried with PromQL, its own query language built around that dimensionality. Prometheus normally pulls metrics from targets over HTTP (discovered via service discovery or static configuration), though a push path via an intermediary gateway exists for batch jobs. A single Prometheus server is self-contained with no distributed-storage dependency, and multiple servers can be combined through hierarchical or horizontal federation.

It's commonly paired with a separate dashboarding tool for visualization and fits teams that need metrics collection, querying, and alerting for services and infrastructure, especially in cloud-native/Kubernetes environments where CNCF tooling is already in use.