Mimir & Grafana Alerting
Scale Prometheus metrics horizontally with Mimir and run unified alerts across sources.
Grafana Mimir is the "M" in LGTM: a horizontally scalable, long-term store for Prometheus metrics. A single Prometheus is bounded by one node's memory and disk, so Mimir accepts metrics via remote_write, shards them across many instances, stores blocks in object storage, and serves PromQL queries over years of data with high availability and multi-tenancy. It descends from Cortex and competes conceptually with Thanos. The point: keep Prometheus as the collector, push to Mimir for scale and retention.
Mimir is a regional power grid that takes output from many local generators (Prometheis) and distributes it reliably at scale; Grafana Alerting is the single control room watching every line and calling the right crew.