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  "description": "A Service Level Indicator (SLI) is a measurement of how well a service is performing on a given dimension, such as availability, latency, throughput, or correctness. SLIs are the raw observables; SLOs are targets set on top of them.\n\n\nCommon SLI types\n\n * Availability: ratio of successful requests to total requests over a window.\n * Latency: proportion of requests served below a threshold (for example, p95 under 200 ms).\n * Throughput: events processed per second; often used for batch and stream",
  "path": "/engineering-glossary/sli-service-level-indicator/",
  "publishedAt": "2026-05-12T18:16:39.000Z",
  "site": "https://sahilkapoor.com",
  "tags": [
    "SLO",
    "Observability",
    "Metrics",
    "Prometheus",
    "Grafana"
  ],
  "textContent": "**A Service Level Indicator (SLI)** is a measurement of how well a service is performing on a given dimension, such as availability, latency, throughput, or correctness. SLIs are the raw observables; SLOs are targets set on top of them.\n\n## Common SLI types\n\n  * **Availability:** ratio of successful requests to total requests over a window.\n  * **Latency:** proportion of requests served below a threshold (for example, p95 under 200 ms).\n  * **Throughput:** events processed per second; often used for batch and stream pipelines.\n  * **Quality / correctness:** proportion of responses that meet a freshness, completeness, or accuracy check.\n  * **Durability:** for storage systems, the probability that data is not lost.\n\n\n\n## Designing a good SLI\n\n  * Measured at a point that reflects the user experience, typically the request boundary closest to the user.\n  * Defined as a ratio with a clear numerator and denominator, so the SLO becomes a single percentage.\n  * Resilient to harmless fluctuations: a single 5xx among 1 million requests should not invalidate the indicator.\n\n\n\n🔗\n\n**Related Terms**\nSLO, Observability, Metrics, Prometheus, Grafana.",
  "title": "SLI",
  "updatedAt": "2026-05-13T19:14:59.490Z"
}