Grafana Loki documentation
Grafana Loki is a set of components that can be composed into a fully featured logging stack.
Unlike other logging systems, Loki is built around the idea of only indexing metadata about your logs: labels (just like Prometheus labels).
Log data itself is then compressed and stored in chunks in object stores such as Amazon Simple Storage Service (S3) or Google Cloud Storage (GCS), or even locally on the filesystem.
A small index and highly compressed chunks simplifies the operation and significantly lowers the cost of Loki.
For more information, see the Loki overview