AZ-400 Implement an instrumentation strategy Practice Question
This AZ-400 practice question tests your understanding of implement an instrumentation strategy. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Your team uses Azure Pipelines to deploy a Node.js application. Recently, deployments have been failing intermittently due to a missing npm package. The pipeline runs successfully on the local agent but fails on the hosted agent. Which instrumentation strategy should you implement to identify the root cause?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable verbose logging for the npm install task and compare the output between pipeline runs.
Option A is correct because enabling verbose logging and comparing the npm install output between agents can reveal differences in package resolution. Option B is wrong because pipeline caching would mask the issue. Option C is wrong because telemetry from the application does not capture build-time dependency issues. Option D is wrong because self-hosted agents would not match the hosted environment.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Replace the hosted agent with a self-hosted agent.
Why it's wrong here
This avoids the problem, not diagnose it.
✗
Configure Application Insights for the Node.js app to monitor runtime errors.
Why it's wrong here
This monitors runtime, not build-time.
✓
Enable verbose logging for the npm install task and compare the output between pipeline runs.
Add a pipeline cache task for npm packages to ensure consistent restore.
Why it's wrong here
Caching may hide the intermittent issue.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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. Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets. 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.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related AZ-400 subnetting questions on CIDR, address ranges, and subnet selection.
Implement an instrumentation strategy — This question tests Implement an instrumentation strategy — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Enable verbose logging for the npm install task and compare the output between pipeline runs. — Option A is correct because enabling verbose logging and comparing the npm install output between agents can reveal differences in package resolution. Option B is wrong because pipeline caching would mask the issue. Option C is wrong because telemetry from the application does not capture build-time dependency issues. Option D is wrong because self-hosted agents would not match the hosted environment.
What should I do if I get this AZ-400 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related AZ-400 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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