Service level objectives overview

Note: This guide only supports Cloud Service Mesh with Istio APIs and doesnot support Google Cloud APIs. For more information see,Cloud Service Mesh overview.

Service Level Objectives (SLOs) are a core tool in the Google service monitoringtoolkit. SLOs can give you a concise and low-noise signal as to the overallhealth of your services. Cloud Service Mesh lets you set SLOs for yourservices, and monitor and alert on your services in terms of those SLOs.

To monitor the health of a service, you need to understand which behaviorsmatter for that service and how to measure and evaluate those behaviors. Aservice level indicator (SLI) is a quantitative measure of some aspect of theservice. Typical SLIs are:

  • Latency: How long it takes to return a response to a request, usually measuredin milliseconds (ms). Latency is typically presented as an aggregate. That is,the raw data is collected over a period of time and calculated as percentiles.Cloud Service Mesh displays a Latency graph on theMetrics pagefor each of your services. The Latency graph shows you the latency over time,which can help you determine a latency threshold or upper bound for a service.
  • Availability: The fraction of the time that a service responds successfully.This is typically presented as a ratio of the number of successful responsesover the total number of responses. The Error rate graph on theMetricspage can help you determine the availability of each service.

An SLO is a target value for a service level that is measured by an SLI. An SLOcan be represented as:SLI ≤ upper_bound orSLI ≥ lower_bound. SLOs aremeasurable goals for performance over a period of time. For example, you mighthave requirements like the following for some of your services:

  • Latency can exceed 300ms in only 5 percent of the requests over a rolling30-day period.
  • The system must have 99% availability measured over a calendar week.

You can set and view SLOs for your services based on their telemetry data on theHealth page. You can then create alerts inCloud Monitoring to warn you if a service isn'tperforming as expected.

What's next

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Last updated 2026-02-19 UTC.