Explain Mimir & Grafana Alerting in Observability

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Grafana (LGTM)

Mimir & Grafana Alerting

Scale Prometheus metrics horizontally with Mimir and run unified alerts across sources.

Grafana Mimir is the "M" in LGTM: a horizontally scalable, long-term store for Prometheus metrics. A single Prometheus is bounded by one node's memory and disk, so Mimir accepts metrics via remote_write, shards them across many instances, stores blocks in object storage, and serves PromQL queries over years of data with high availability and multi-tenancy. It descends from Cortex and competes conceptually with Thanos. The point: keep Prometheus as the collector, push to Mimir for scale and retention.

Mimir is a regional power grid that takes output from many local generators (Prometheis) and distributes it reliably at scale; Grafana Alerting is the single control room watching every line and calling the right crew.

Key Concepts

Grafana Alerting unifies alert rules across all these sources. Rather than each backend owning its own alerting, Grafana evaluates rules (PromQL, LogQL, and more) centrally, manages alert state, and routes notifications through contact points and notification policies — conceptually similar to Alertmanager but spanning every data source Grafana can query. Together, Mimir provides the durable metric backbone and Grafana Alerting provides one consistent alerting and routing experience.

What the interviewer is probing.

What the interviewer is probing.

1. "What problem does Mimir solve?" *Probing:* the purpose. *Stalls:* "Storage." *Moves up:* long-term, horizontally scalable, multi-tenant storage for Prometheus metrics with a global query view.

1. "What problem does Mimir solve?"

2. "What changed with unified Grafana alerting?" *Probing:* currency. *Stalls:* "Nothing." *Moves up:* one alerting system across data sources, replacing the per-dashboard legacy alerts and aligning with Alertmanager routing.

2. "What changed with unified Grafana alerting?"

3. "What is multi-tenancy useful for?" *Probing:* the practical angle. *Stalls:* "Isolation." *Moves up:* separating teams or customers with their own limits and retention on shared infrastructure.

3. "What is multi-tenancy useful for?"

4. "How do you avoid duplicate alerts across tools?" *Probing:* the operational point. *Stalls:* "You cannot." *Moves up:* decide one system owns each alert — two systems paging on the same symptom is how trust in alerting is lost.

4. "How do you avoid duplicate alerts across tools?"