The answer is approximately 43.2 minutes of allowed downtime. This is correct because a 99.9% Service Level Objective (SLO) permits 0.1% unavailability over the measurement period. For a 30-day month, total minutes are 30 × 24 × 60 = 43,200, and 0.1% of that equals 43.2 minutes. On the Google Cloud Digital Leader exam, this SLO downtime calculation tests your grasp of availability math and how SLOs define acceptable risk—a common trap is forgetting to convert days to minutes or misplacing the decimal. A quick memory tip: think of 99.9% as “three nines,” which allows roughly 43 minutes of downtime in a month, or about 7 minutes per week.
Cloud Digital Leader Scaling with Google Cloud operations Practice Question
This GCDL practice question tests your understanding of scaling with google cloud operations. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company's web service has a Service Level Objective (SLO) of 99.9% monthly availability. In a 30-day month, how many minutes of downtime are allowed before the SLO is violated?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
~43.2 minutes
The SLO of 99.9% monthly availability means the service can be unavailable for 0.1% of the total monthly time. In a 30-day month, total minutes are 30 × 24 × 60 = 43,200 minutes. 0.1% of 43,200 minutes is 43.2 minutes, so option B is correct.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
~4.3 minutes
Why it's wrong here
4.3 minutes corresponds to 99.99% (four nines) availability, not 99.9% (three nines). Three nines allows approximately 10× more downtime.
✓
~43.2 minutes
Why this is correct
99.9% availability = 0.1% downtime. In a 30-day month (43,200 minutes), 0.1% = 43.2 minutes of allowed downtime — the classic 'three nines' error budget.
Related concept
Read the scenario before looking for a memorised answer.
✗
~7.2 hours
Why it's wrong here
7.2 hours corresponds to approximately 99% availability (two nines). 99.9% is an order of magnitude more restrictive.
✗
~8.6 hours
Why it's wrong here
8.6 hours is roughly 99% availability. 99.9% availability allows only ~43 minutes of downtime per month.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 99.9% with 99.99% (four nines) and incorrectly calculate ~4.3 minutes, or they mistakenly compute 0.1% of 30 days in hours (0.072 hours) and then misread it as 7.2 hours.
Detailed technical explanation
How to think about this question
Under the hood, SLOs are often measured using monitoring tools like Cloud Monitoring (Stackdriver) which track uptime checks and calculate error budgets. The error budget for a 99.9% SLO over a 30-day month is exactly 43.2 minutes; exceeding this consumes the budget and triggers escalation or engineering response. In real-world scenarios, teams must account for planned maintenance windows and exclude them from downtime calculations if they are within the SLO definition.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this GCDL question in full detail.
Scaling with Google Cloud operations — This question tests Scaling with Google Cloud operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ~43.2 minutes — The SLO of 99.9% monthly availability means the service can be unavailable for 0.1% of the total monthly time. In a 30-day month, total minutes are 30 × 24 × 60 = 43,200 minutes. 0.1% of 43,200 minutes is 43.2 minutes, so option B is correct.
What should I do if I get this GCDL question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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