Mimir

Grafana Mimir is an open-source, horizontally scalable, multi-tenant time series database (TSDB) designed for long-term storage of Prometheus and OpenTelemetry metrics. Announced by Grafana Labs in 2022 and released under the AGPLv3 license, Mimir targets organizations that need to store and query metrics at massive scale—tested to 1 billion active series—while maintaining high availability and strong multi-tenancy. It is best suited for mid-to-large teams already invested in the Prometheus ecosystem who require a centralized metrics backend that can replace or augment individual Prometheus servers, and who have the operational capacity to manage a clustered distributed system. Mimir integrates natively with Grafana for visualization and monitoring, and is the backbone of Grafana Cloud Metrics, the vendor's managed service.

Mimir achieves its scale and performance through a horizontally scalable, clustered architecture that separates ingestion, storage, and query paths. It is 100% Prometheus compatible, supporting remote write, PromQL, and alerting, and can also ingest metrics from InfluxDB, OpenTelemetry, Graphite, and Datadog agents. Long-term storage is offloaded to object stores such as S3, GCS, Azure Blob Storage, or OpenStack Swift, rather than requiring local persistent disks. The Mimir 3.0 release introduced a decoupled read/write architecture that eliminates cross-path dependencies, and a new streaming query engine that reduces memory usage by processing query results incrementally instead of loading entire datasets into RAM. Grafana Labs reports that large internal clusters saw up to 15% lower resource usage after upgrading to 3.0, while maintaining higher reliability and query performance.

Mimir competes directly with VictoriaMetrics and Thanos, two other popular open-source Prometheus-compatible backends. Compared to VictoriaMetrics, Mimir is considered more complex to operate, especially for small teams, but offers stronger multi-tenancy and isolation features. VictoriaMetrics stores data on local persistent disks (block storage), while Mimir relies on object storage (S3, GCS, etc.), which can simplify capacity planning but introduces different latency characteristics. Thanos also uses object storage and allows users to keep Prometheus as the ingester, whereas Mimir forces the use of its own ingesters, which some operators see as a trade-off in flexibility. Mimir's development is led by Grafana Labs, giving it tight integration with Grafana and a large corporate backer, while VictoriaMetrics is developed by a smaller independent team. All three projects are open source, but Mimir's AGPLv3 license is more restrictive than VictoriaMetrics' Apache 2.0 license.

The primary trade-off with Mimir is its operational complexity: it requires configuring and running a multi-component cluster (ingesters, distributors, queriers, compactors, etc.), which is not suitable for small teams or simple use cases. The reliance on ingesters (rather than allowing Prometheus to serve as the ingester, as Thanos does) is a specific architectural constraint that some users find limiting. While Mimir is free and open source, running it at scale demands significant infrastructure and expertise; the managed Grafana Cloud Metrics service is an alternative for teams that want Mimir's capabilities without the operational overhead. Additionally, as dashboards and data volumes grow, Grafana itself can slow down and require more powerful machines, adding cost and complexity—though this is a Grafana concern rather than a Mimir-specific one. Finally, Mimir's AGPLv3 license may be a consideration for organizations with strict policies around copyleft licensing.

Free open-source version available under AGPLv3 license. Managed cloud version available as Grafana Cloud Metrics with usage-based pricing (no public fixed tiers listed).