groups:
  - name: nereus-api
    rules:
      - alert: NereusAPIHighErrorRate
        expr: |
          sum(rate(nereus_http_requests_total{path=~"/api/v1/.*",status=~"5.."}[2m]))
          /
          clamp_min(sum(rate(nereus_http_requests_total{path=~"/api/v1/.*"}[2m])), 0.001)
          > 0.05
        for: 1m
        labels:
          severity: critical
        annotations:
          summary: Nereus API error rate exceeds 5 percent
          description: The API has returned more than 5 percent HTTP 5xx responses for one minute.

      - alert: NereusAPIHighLatency
        expr: |
          histogram_quantile(
            0.95,
            sum by (le) (rate(nereus_http_request_duration_seconds_bucket{path=~"/api/v1/.*"}[5m]))
          ) > 1
        for: 2m
        labels:
          severity: warning
        annotations:
          summary: Nereus API p95 latency exceeds one second
          description: The API p95 request duration has exceeded one second for two minutes.

      - alert: NereusAPIReadinessFailing
        expr: sum(rate(nereus_http_requests_total{path="/readyz",status="503"}[2m])) > 0
        for: 1m
        labels:
          severity: critical
        annotations:
          summary: Nereus API cannot reach its database
          description: Readiness requests have returned HTTP 503 for one minute.

      - alert: NereusAPIDown
        expr: up{job="nereus-api"} == 0
        for: 1m
        labels:
          severity: critical
        annotations:
          summary: Prometheus cannot scrape the Nereus API
          description: The Nereus API metrics endpoint has been unreachable for one minute.