How do you scale Prometheus for long-term storage and high availability (Thanos, Cortex, Mimir)? [Intermediate]
Answer
To scale Prometheus for long-term storage and HA, I run at least two Prometheus replicas per shard, use remote write or sidecars, and query long-term data through systems such as Thanos, Cortex, or Mimir. The exact choice depends on tenancy, scale, and operational model.
Technical explanation
Prometheus itself is single-node per shard, so horizontal scale usually means functional sharding and federation or remote-write architectures.
Thanos adds sidecar upload, object storage, global querying, compaction, and deduplication around Prometheus.
Cortex and Mimir are horizontally scalable, multi-tenant metrics backends designed for remote-write ingestion and large-scale querying.
Hands-on example
Example design: run two Prometheus replicas for each Kubernetes cluster. Remote write to Mimir for 13-month retention. Use Grafana to query Mimir for historical dashboards and local Prometheus for low-latency rule evaluation. Configure replica labels for deduplication.
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