PCDE Applying Site Reliability Engineering Practices to a Service — 10 Questions

Question 1

An SRE team wants to define an SLI for service availability. Which metric correctly represents the availability SLI?

Accepted Answer

Total requests that succeed / Total requests. Availability as an SLI is measured as the proportion of successful requests to total requests. Option A correctly defines this as 'Total requests that succeed / Total requests'. Option B is incorrect because it measures latency (response time within 200 ms), not availability. Option C is a measure of uptime, not service availability from the user's perspective. Option D only counts errors, which is not a ratio.

Answer

Total requests that complete within 200 ms / Total requests

Answer

Total minutes the service is up / Total minutes in the window

Answer

Number of requests that return a 5xx status code

Question 2

A service has an SLO of 99.9% availability over a 30-day month. What is the error budget in minutes for that month?

Accepted Answer

43.2 minutes. Error budget = (100% - SLO) * total time. 0.1% of 43,200 minutes (30 days) is 43.2 minutes. Rounded to 43 minutes.

Answer

144 minutes

Answer

4.32 minutes

Answer

432 minutes

Question 3

An engineer needs to set up alerting for error budget burn rate. For a fast burn alert, which burn rate multiplier and evaluation window are recommended?

Accepted Answer

1-hour window, 14x burn rate. Fast burn alert uses a 1-hour window and 14x burn rate. Slow burn uses 6-hour window and 5x burn rate.

Answer

6-hour window, 5x burn rate

Answer

1-hour window, 5x burn rate

Answer

6-hour window, 14x burn rate

Question 4

A team wants to reduce toil by automating a manual process that generates a report from Cloud Logging logs and emails it weekly. Which solution is most cost-effective and requires minimal operational overhead?

Accepted Answer

Cloud Scheduler + Cloud Functions. Cloud Scheduler triggers a Cloud Function or runs a query in BigQuery, but the most straightforward serverless option is a Cloud Function triggered by Cloud Scheduler. Cloud Composer is heavy for a simple report. Cloud Run requires containerization. Cloud Build is for CI/CD.

Answer

Cloud Run job manually started

Answer

Cloud Build trigger on schedule

Answer

Cloud Composer (Airflow) DAG

Question 5

During an incident, the incident commander identifies a need to scale up a managed instance group. Which IAM role should be granted to the on-call engineer to allow them to modify the instance group?

Accepted Answer

roles/compute.instanceAdmin.v1. Compute Instance Admin (roles/compute.instanceAdmin.v1) allows full control over instances and instance groups, including modifying MIGs. Instance Admin (basic) is restricted. Compute Admin is broader but includes other resources. Security Admin does not have compute permissions.

Answer

roles/compute.admin

Answer

roles/compute.securityAdmin

Answer

roles/compute.instanceAdmin (basic)

Question 6

A service has an SLO based on request latency: 99% of requests must complete under 500ms over a 28-day window. The team wants to monitor the error budget burn rate. Which Cloud Monitoring SLO type and configuration should be used?

Accepted Answer

Request-based SLO: good request count / valid request count with threshold 500ms. A request-based SLO with a good-request-count/valid-request-count metric is appropriate for latency SLIs. The threshold is set at 500ms. Window-based SLOs are for uptime, not latency.

Answer

Window-based SLO: good minutes / total minutes with threshold 500ms

Answer

Request-based SLO: good request count / total request count with threshold 500ms

Answer

Window-based SLO: good requests / total requests with threshold 500ms

Question 7

Which of the following best describes 'toil' in SRE?

Accepted Answer

Manual, repetitive work that provides no enduring value and scales linearly with service growth. Toil is work that is manual, repetitive, automatable, and does not provide enduring value. It scales with service growth.

Answer

Work that is creative and requires deep domain knowledge

Answer

Automating infrastructure provisioning

Answer

Incident response and on-call duties

Question 8

A team wants to implement chaos engineering on Google Kubernetes Engine (GKE) to test resilience against pod failures. Which tool is designed for injecting faults into GKE clusters?

Accepted Answer

Chaos Mesh on GKE. Chaos Mesh is an open-source chaos engineering platform for Kubernetes, including GKE. It can inject pod failures, network delays, etc. Traffic Director fault injection is for service mesh, not GKE-native.

Answer

GKE Node Auto-Repair

Answer

Traffic Director fault injection

Answer

Cloud Armor

Question 9

An SRE team uses Cloud Monitoring SLOs with an error budget policy. They want to receive an alert when the error budget is exhausted at a rate that would exhaust it in 1 hour (fast burn). The SLO is 99.9% over 30 days. The error budget is 43.2 minutes. What burn rate threshold should be used?

Accepted Answer

14. In Google SRE practice, a fast burn alert uses a 1-hour window and a burn rate threshold of 14. This means the alert fires when the error rate exceeds 14 times the allowable rate, indicating that the budget is being consumed rapidly. At a burn rate of 14, the budget would be exhausted in 30 days / 14 ≈ 2.14 days. The question's reference to 'exhaust it in 1 hour' refers to the alert's lookback window (1 hour), not the actual time to budget exhaustion. A burn rate of 720 would exhaust the budget in 1 hour, but that is not a standard alert threshold. Therefore, the correct answer is 14.

Answer

5

Answer

720

Answer

1

Question 10

During a blameless postmortem, the team uses the '5 Whys' technique to identify root causes. What is the primary purpose of this technique?

Accepted Answer

To iteratively ask 'why' to uncover the root cause. 5 Whys is a root cause analysis technique used to uncover the underlying causes of an incident, not to assign blame or find contributors superficially.

Answer

To estimate the cost of the incident

Answer

To identify the immediate superficial cause of the incident

Answer

To determine which team member made an error