PCDE Applying Site Reliability Engineering Practices to a Service Practice Test 2 — 15 Questions

Question 1

A site reliability engineer is defining an SLO for a service that processes user uploads. The team wants to measure success as the proportion of uploads completed within 2 seconds. Which type of SLI should they use?

Accepted Answer

Latency-based SLI measuring proportion of requests under a threshold. This scenario describes a request-based SLI where each upload is a request, and success is defined by latency being under a threshold (2 seconds). Request-based SLIs count good requests (those meeting the criteria) over total requests.

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Throughput-based SLI measuring requests per second

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Freshness-based SLI measuring time since last successful upload

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Availability-based SLI using successful/total requests

Question 2

A team's SLO for availability is 99.9% over a 30-day window. They have consumed 80% of their error budget halfway through the month. What is the remaining allowed downtime for the rest of the month?

Accepted Answer

About 8 minutes 38 seconds. Total error budget = 100% - 99.9% = 0.1% of 30 days = 43.2 minutes (0.1% * 30 * 1440). 80% consumed means 20% remains: 0.2 * 43.2 = 8.64 minutes, approximately 8 minutes 38 seconds.

Answer

About 17 minutes 17 seconds

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About 34 minutes 34 seconds

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About 43 minutes 12 seconds

Question 3

You are configuring error budget burn rate alerts for an SLO with a 30-day window. The SLO target is 99.9%. You want to alert if the error budget is projected to be fully consumed in 2 hours, using a fast burn rate. Which alerting policy configuration should you use?

Accepted Answer

Burn rate threshold: 14, lookback window: 1 hour. Fast burn alert: burn rate > 14x for 1-hour window. If full budget consumed in 2 hours, burn rate = (30 days * 1440 min/day) / (2 hours * 60 min/hour) = 43200 / 120 = 360. But the standard fast burn alert uses a 1-hour window and a burn rate threshold of 14, which corresponds to consuming the budget in ~2 hours (43200/14 ≈ 3085 min ≈ 2.14 days). To alert on 2-hour consumption, you need a custom alert with a burn rate of 14 and a lookback window of 1 hour (the standard fast burn configuration). That alert triggers when the rate of budget consumption would exhaust the budget in ~2 hours if sustained.

Answer

Burn rate threshold: 14, lookback window: 6 hours

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Burn rate threshold: 5, lookback window: 1 hour

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Burn rate threshold: 5, lookback window: 6 hours

Question 4

An SRE team wants to reduce toil associated with manual database schema migrations. They currently run SQL scripts manually during maintenance windows. Which Google Cloud service is most appropriate to automate this process in a repeatable way?

Accepted Answer

Cloud Build. Cloud Build is a CI/CD platform that can execute SQL migration scripts as part of a build pipeline. It integrates with Cloud Source Repositories and can trigger on schema changes. Cloud Functions and Workflows are more for event-driven workflows, not typical for database migrations.

Answer

Cloud Scheduler

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Workflows

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Cloud Functions

Question 5

During a blameless postmortem after an incident, the team identified that the root cause was a misconfigured load balancer health check. Which practice should the team prioritize to prevent recurrence?

Accepted Answer

Add a test in CI/CD to validate health check configuration. A blameless postmortem focuses on finding contributing factors and creating action items to improve the system. The action item should be to fix the health check configuration and automate validation. Implementing a runbook for future incidents is reactive, not preventive. Creating a rollback plan is also reactive.

Answer

Create a rollback plan for health check changes

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Schedule a weekly manual review of load balancer settings

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Write a runbook for future load balancer incidents

Question 6

Which Google Cloud service can be used to inject artificial delays into HTTP traffic to test service resilience?

Accepted Answer

Traffic Director. Traffic Director supports fault injection, including delay and abort faults, for HTTP traffic. This is used in chaos engineering to test service resilience. Chaos Mesh is for Kubernetes, but Traffic Director is the managed service for traffic management.

Answer

Cloud Endpoints

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Cloud Armor

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Cloud Load Balancing

Question 7

A team uses Cloud Monitoring SLO monitoring with a request-based SLI. The SLO is defined as the proportion of requests returning HTTP 200 with latency under 500ms over a 30-day window. They notice that the SLO is being violated due to a slow increase in latency from a specific backend. Which alerting strategy will best detect this gradual degradation early?

Accepted Answer

Slow burn alert with burn rate 5 and 6-hour window. Slow burn alerts (burn rate threshold ~5, lookback window ~6 hours) detect gradual budget consumption that would exhaust the budget over several days. Fast burn alerts (14x, 1h) catch rapid budget consumption. The scenario describes a slow increase, so a slow burn alert is appropriate.

Answer

Alert on any single request exceeding 500ms

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Fast burn alert with burn rate 14 and 1-hour window

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Alert when average latency exceeds 500ms for 1 minute

Question 8

An SRE team wants to reduce toil by automating the response to common alert notifications. For example, when a disk usage alert fires, they want to automatically run a script to clean up temporary files. Which Google Cloud service is best suited for this?

Accepted Answer

Cloud Functions. Cloud Functions can be triggered by Cloud Monitoring alerts via Pub/Sub and execute arbitrary code (e.g., script to clean disk). This is a common pattern for automated remediation. Workflows could orchestrate multiple steps but adds complexity. Cloud Build is CI/CD, not event-driven. Cloud Scheduler is for scheduled tasks.

Answer

Cloud Build

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Workflows

Answer

Cloud Scheduler

Question 9

What is the primary purpose of an error budget?

Accepted Answer

To balance reliability and innovation by allowing a controlled amount of failure. Error budgets are the permissible amount of unreliability (100% - SLO). They allow teams to balance reliability with feature velocity: if budget remains, teams can deploy new features; if depleted, focus on reliability.

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To measure team performance for annual reviews

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To define the maximum acceptable downtime in a contract

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To track the total number of errors in a system

Question 10

An e-commerce platform wants to implement chaos engineering on its Google Kubernetes Engine cluster to test resilience against network latency. Which tool is specifically designed for this purpose on GKE?

Accepted Answer

Chaos Mesh. Chaos Mesh is an open-source chaos engineering platform for Kubernetes. It can inject various faults including network latency, and is available on GKE. Traffic Director fault injection is for service mesh, not directly for GKE pods. Cloud Functions is not for Kubernetes.

Answer

Traffic Director fault injection

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Cloud Functions

Answer

Cloud Build

Question 11

Your microservice has an SLO of 99.95% availability over 30 days. A 5-minute outage occurs. The error budget consumption rate for that hour is extremely high. You want to alert on this quick consumption using a fast burn alert. What burn rate threshold and lookback window should you configure to detect if the budget would be exhausted in under 2 hours?

Accepted Answer

Burn rate: 14, Window: 1 hour. The question asks for a fast burn alert configuration to detect if the error budget would be exhausted in under 2 hours. However, the standard Google SRE fast burn alert uses a burn rate of 14 over a 1-hour window, which corresponds to budget exhaustion in approximately 30/14 ≈ 2.14 days, not under 2 hours. The 5-minute outage in one hour consumes 5 minutes of the 21.6-minute budget (23%), resulting in a burn rate of 5 / (21.6/720) ≈ 166.7, far exceeding 14. Thus, the fast burn alert would trigger immediately. Options A and C (burn rate 5) would not fire because the burn rate is higher than 5. Option B (window 6 hours) would delay the alert and might not capture the spike quickly enough. Therefore, option D (burn rate 14, window 1 hour) is the correct configuration, as it is the standard fast burn alert that catches such rapid consumption.

Answer

Burn rate: 5, Window: 1 hour

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Burn rate: 14, Window: 6 hours

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Burn rate: 5, Window: 6 hours

Question 12

A team wants to create an SLO for a batch data pipeline that processes files hourly. They want to measure whether each batch completes successfully within the hour. Which type of SLI should they use?

Accepted Answer

Window-based SLI measuring good minutes over total minutes. For batch or sliding window data, a window-based SLI is appropriate: it counts good minutes (or windows) where the pipeline succeeded within the time window, divided by total minutes. Request-based SLIs are for individual request/response pairs.

Answer

Latency-based SLI measuring p99 of file processing time

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Request-based SLI measuring good requests over total requests

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Availability SLI based on successful API calls

Question 13

An SRE team wants to implement error budget burn rate alerts for a service with SLO 99.9% over 30 days. They need to be notified both when the error budget is being consumed rapidly (full consumption in ~2 hours) and when it is being consumed slowly (full consumption in ~6 days). Which two alert configurations should they use? (Choose 2)

Accepted Answer

Burn rate threshold: 14, lookback window: 1 hour. Standard best practice: fast burn alert: burn rate 14, window 1 hour (consumes budget in ~2 days actual, but for 2 hours need custom? Actually 14x over 1 hour means budget would be consumed in ~2.14 days. For 2 hours, you'd need a higher threshold, but the question likely expects the standard fast and slow burn pair. Slow burn: burn rate 5, window 6 hours (consumes budget in ~6 days).

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Burn rate threshold: 2, lookback window: 1 hour

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Burn rate threshold: 10, lookback window: 1 hour

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Burn rate threshold: 14, lookback window: 6 hours

Question 14

A team is conducting a blameless postmortem after a production incident. Which three actions are part of an effective blameless postmortem process? (Choose 3)

Accepted Answer

Define action items with specific owners and due dates. Blameless postmortems focus on identifying contributing factors, using techniques like 5 Whys, and defining action items with owners. Assigning blame, punishing, or ignoring minor factors are not part of the process.

Answer

Assign blame to the individual who made the error

Answer

Punish the on-call engineer for missing the alert

Question 15

A team wants to reduce toil in their operations. Which two of the following are characteristics of toil according to Google SRE principles? (Choose 2)

Accepted Answer

Work that is manual and repetitive. Toil is manual, repetitive, automatable, devoid of enduring value, and scales linearly with service growth. Work that is creative or strategic is not toil. Tasks that require deep analysis are not toil.

Answer

Work that provides enduring value for the service

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Work that is completely automated already

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Work that requires creative problem-solving