Cortex vs Thanos: Which Long-Term Prometheus?
Cortex is a horizontally scalable, multi-tenant Prometheus-as-a-service backend; Thanos extends existing Prometheus servers with global query and object-store retention.
Cortex centralizes ingestion into a clustered, multi-tenant service that stores metrics in object storage, ideal for offering metrics as a managed platform. Thanos adds sidecars and components alongside your existing Prometheus instances to provide a global query view and long-term retention with minimal disruption. Cortex wins for large multi-tenant platforms; Thanos wins for augmenting existing Prometheus deployments.
| Cortex | Thanos | |
|---|---|---|
| Approach | Centralized service | Sidecar augmentation |
| Multi-tenancy | First-class | Possible, less central |
| Adoption | Replace ingestion | Keep existing Prometheus |
| Storage | Object store | Object store |
| Best for | Metrics platforms | Augmenting Prometheus |
Use case and architecture
Cortex suits organizations building a centralized, multi-tenant metrics platform with strong isolation. Thanos suits teams that already run Prometheus and want global querying and cheap long-term storage without re-architecting ingestion.
Ops and CI fit
Both are distributed systems with several components and object storage; Cortex is more centralized, Thanos more incremental. Their components are built and integration-tested in CI, where faster managed runners shorten builds and multi-component tests.
The verdict
Building a centralized multi-tenant metrics platform: Cortex (or its Mimir successor). Augmenting existing Prometheus with global query and retention: Thanos. Pick by whether you replace or extend your current Prometheus.