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PROFESSIONAL-CLOUD-DEVOPS-ENGINEER · Question #36

You are responsible for the reliability of a high-volume enterprise application. A large number of users report that an important subset of the application's functionality "a data intensive reporting

The correct answer is B. As the proportion of report generation requests that result in a successful response. An availability Service Level Indicator (SLI) for the report generation feature should be defined as the proportion of successful requests for that feature.

Submitted by devops_kid· Apr 18, 2026Applying site reliability engineering principles to a service

Question

You are responsible for the reliability of a high-volume enterprise application. A large number of users report that an important subset of the application's functionality "a data intensive reporting feature" is consistently failing with an HTTP 500 error. When you investigate your application's dashboards, you notice a strong correlation between the failures and a metric that represents the size of an internal queue used for generating reports. You trace the failures to a reporting backend that is experiencing high I/O wait times. You quickly fix the issue by resizing the backend's persistent disk (PD). How you need to create an availability Service Level Indicator (SLI) for the report generation feature. How would you define it?

Options

  • AAs the I/O wait times aggregated across all report generation backends
  • BAs the proportion of report generation requests that result in a successful response
  • CAs the application's report generation queue size compared to a known-good threshold
  • DAs the reporting backend PD throughout capacity compared to a known-good threshold

How the community answered

(26 responses)
  • A
    8% (2)
  • B
    73% (19)
  • C
    15% (4)
  • D
    4% (1)

Why each option

An availability Service Level Indicator (SLI) for the report generation feature should be defined as the proportion of successful requests for that feature.

AAs the I/O wait times aggregated across all report generation backends

I/O wait times are an internal system metric that can contribute to availability issues, but it is not a direct measure of availability from the user's perspective, making it a good diagnostic metric but not an SLI.

BAs the proportion of report generation requests that result in a successful responseCorrect

An availability SLI measures the percentage of valid requests that receive a valid response within a specific measurement window. For a reporting feature, the most direct measure of its availability from a user's perspective is whether their requests for reports succeed (e.g., return HTTP 200 OK) or fail (e.g., HTTP 500 error), making the proportion of successful responses the ideal SLI.

CAs the application's report generation queue size compared to a known-good threshold

The report generation queue size is an internal health metric that can indicate performance or backlog issues, but it does not directly represent the success or failure rate of user requests for the feature.

DAs the reporting backend PD throughout capacity compared to a known-good threshold

PD throughput capacity is an infrastructure metric and a potential cause of performance issues, but it is not a direct user-centric measure of the availability of the reporting feature itself.

Concept tested: Defining Availability Service Level Indicator (SLI)

Source: https://sre.google/sre-book/monitoring-alerting/#what-to-measure-in-an-sli

Topics

#SLI (Service Level Indicator)#Availability#SRE Principles#Monitoring Strategy

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