Thanos is a set of components that can be composed into a highly available
metric system with unlimited storage capacity, which can be added seamlessly on
top of existing Prometheus deployments.

Thanos leverages the Prometheus 2.0 storage format to cost-efficiently store
historical metric data in any object storage while retaining fast query
latencies. Additionally, it provides a global query view across all Prometheus
installations and can merge data from Prometheus HA pairs on the fly.

WWW: https://thanos.io/