AZ-400 Design and implement a DevOps infrastructure Practice Question
This AZ-400 practice question tests your understanding of design and implement a devops infrastructure. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Exhibit
Metrics for WebApp1 (last 24 hours):
Time | Requests | HTTP 5xx | AverageResponseTime
10:00 AM | 1200 | 0 | 200 ms
10:05 AM | 1500 | 0 | 210 ms
10:10 AM | 1800 | 0 | 220 ms
10:15 AM | 2000 | 0 | 230 ms
10:20 AM | 2200 | 0 | 240 ms
10:25 AM | 2500 | 0 | 250 ms
10:30 AM | 3000 | 15 | 500 ms
10:35 AM | 2800 | 12 | 480 ms
10:40 AM | 2600 | 8 | 450 ms
10:45 AM | 2400 | 3 | 400 ms
Refer to the exhibit. You monitor an Azure App Service web app. At 10:30 AM, you observe a spike in HTTP 5xx errors and response time. Based on the metrics, what is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Metrics for WebApp1 (last 24 hours):
Time | Requests | HTTP 5xx | AverageResponseTime
10:00 AM | 1200 | 0 | 200 ms
10:05 AM | 1500 | 0 | 210 ms
10:10 AM | 1800 | 0 | 220 ms
10:15 AM | 2000 | 0 | 230 ms
10:20 AM | 2200 | 0 | 240 ms
10:25 AM | 2500 | 0 | 250 ms
10:30 AM | 3000 | 15 | 500 ms
10:35 AM | 2800 | 12 | 480 ms
10:40 AM | 2600 | 8 | 450 ms
10:45 AM | 2400 | 3 | 400 ms
A
The web app reached its scaling limit and could not handle the increased load.
Correct. The requests increased steadily, and at 10:30 AM, the app started returning errors and slowing down, indicating it hit a capacity bottleneck.
B
A deployment of new code at 10:30 AM introduced a bug.
Why wrong: Incorrect. The metrics show a gradual increase in requests before 10:30 AM, suggesting a scaling issue rather than a code change.
C
A DDoS attack started at 10:30 AM.
Why wrong: Incorrect. While possible, the gradual increase in requests before the spike suggests organic load, not an attack.
D
A database outage caused the errors and slow responses.
Why wrong: Incorrect. There is no direct evidence of a database issue; the pattern suggests a scaling problem.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The web app reached its scaling limit and could not handle the increased load.
The request count increased gradually from 1200 to 2500 before the errors started at 10:30 AM. The sharp rise in errors and response time coinciding with peak load indicates the app reached its capacity limit (e.g., instance count or plan limits).
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.
✓
The web app reached its scaling limit and could not handle the increased load.
Why this is correct
Correct. The requests increased steadily, and at 10:30 AM, the app started returning errors and slowing down, indicating it hit a capacity bottleneck.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
A deployment of new code at 10:30 AM introduced a bug.
Why it's wrong here
Incorrect. The metrics show a gradual increase in requests before 10:30 AM, suggesting a scaling issue rather than a code change.
✗
A DDoS attack started at 10:30 AM.
Why it's wrong here
Incorrect. While possible, the gradual increase in requests before the spike suggests organic load, not an attack.
✗
A database outage caused the errors and slow responses.
Why it's wrong here
Incorrect. There is no direct evidence of a database issue; the pattern suggests a scaling problem.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
Incorrect. The metrics show a gradual increase in requests before 10:30 AM, suggesting a scaling issue rather than a code change.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-400 question in full detail.
Identify which AZ-400 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Design and implement a DevOps infrastructure — This question tests Design and implement a DevOps infrastructure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The web app reached its scaling limit and could not handle the increased load. — The request count increased gradually from 1200 to 2500 before the errors started at 10:30 AM. The sharp rise in errors and response time coinciding with peak load indicates the app reached its capacity limit (e.g., instance count or plan limits).
What should I do if I get this AZ-400 question wrong?
Identify which AZ-400 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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