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Metrics & Monitoring — Simple#

Problem statement (interviewer prompt)

Design a metrics + monitoring platform (Prometheus / Datadog): collect ~10B time-series samples/day with bounded cardinality, support flexible query/aggregation, evaluate alerting + recording rules, and serve dashboards with sub-second latency.

flowchart LR
  APP[Service]
  AG[Exporter / Agent]
  TSDB[(TSDB<br/>Prometheus / Mimir)]
  G[Grafana]
  AL[Alertmanager]
  PD[PagerDuty]
  APP --> AG --> TSDB --> G
  TSDB --> AL --> PD

    classDef client fill:#dbeafe,stroke:#1e40af,stroke-width:1px,color:#0f172a;
    classDef edge fill:#cffafe,stroke:#0e7490,stroke-width:1px,color:#0f172a;
    classDef service fill:#fef3c7,stroke:#92400e,stroke-width:1px,color:#0f172a;
    classDef datastore fill:#fee2e2,stroke:#991b1b,stroke-width:1px,color:#0f172a;
    classDef cache fill:#fed7aa,stroke:#9a3412,stroke-width:1px,color:#0f172a;
    classDef queue fill:#ede9fe,stroke:#5b21b6,stroke-width:1px,color:#0f172a;
    classDef compute fill:#d1fae5,stroke:#065f46,stroke-width:1px,color:#0f172a;
    classDef storage fill:#e5e7eb,stroke:#374151,stroke-width:1px,color:#0f172a;
    classDef external fill:#fce7f3,stroke:#9d174d,stroke-width:1px,color:#0f172a;
    classDef obs fill:#f3e8ff,stroke:#6b21a8,stroke-width:1px,color:#0f172a;
    class APP,AG service;
    class TSDB datastore;
    class G,AL,PD obs;