Thanos
Highly available Prometheus setup
The Lens
By Erik Loyd, SaaS CEO and former COO/CFO of an AWS Premier Partner.
Updated Mar 2026
Thanos extends Prometheus into a highly available, horizontally scalable monitoring system with long-term retention and cross-cluster querying. It sits on top of your existing Prometheus setup and adds what Prometheus deliberately left out.
You keep your Prometheus instances. Thanos adds a global query view across all of them, long-term storage in object storage (S3, GCS, Azure Blob), downsampling for historical queries, and high availability through deduplication. It's not a replacement; it's the scaling layer.
Apache 2.0, CNCF project. Production-proven at companies running hundreds of Prometheus instances.
The catch: Thanos adds real operational complexity. You're running Thanos Sidecar, Store Gateway, Compactor, Query Frontend. Each is a separate component to deploy and monitor. The irony of needing monitoring for your monitoring system is not lost on anyone. If you have fewer than 3 Prometheus instances, you probably don't need this yet.
Free vs Self-Hosted vs Paid
fully freeFully open source under Apache 2.0. No paid tier from the Thanos project itself.
Self-hosted costs:
- Compute: 3-5 additional containers (Sidecar, Store, Compactor, Query, Query Frontend). Minimal CPU/memory per component, maybe $50-100/mo in cloud resources for a small setup.
- Object storage: S3/GCS costs for long-term metrics. Highly variable; a moderate setup might run $20-50/mo for storage, less with downsampling.
- Total: $70-150/mo for a small-to-medium Thanos deployment on top of existing Prometheus.
Managed alternatives: Grafana Cloud, Chronosphere, and others offer managed Prometheus-compatible storage that solves the same problems without running Thanos yourself.
Free software. Budget $70-150/mo for infrastructure on a small-to-medium deployment.
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