- A
Heartbeat | where TimeGenerated < ago(20m) | summarize LastSeen = max(TimeGenerated) by Computer
Why wrong: This can return computers that also sent a recent heartbeat, because the newer data is filtered out before summarizing.
- B
Heartbeat | summarize LastSeen = max(TimeGenerated) by Computer | where LastSeen < ago(20m)
This query first finds the latest heartbeat per computer and then filters for machines whose latest timestamp is older than 20 minutes. That matches the operational requirement exactly and avoids false positives caused by filtering before summarization.
- C
Heartbeat | summarize count() by Computer | where count_ < 20
Why wrong: Heartbeat count does not indicate when the last record was received, so a low count does not prove the computer has been silent for 20 minutes.
- D
Heartbeat | where TimeGenerated > ago(20m) | summarize LastSeen = max(TimeGenerated) by Computer
Why wrong: This query shows machines that have had recent heartbeats, which is the opposite of the requested output.
AZ-104 Monitor and Maintain Azure Resources Practice Question
This AZ-104 practice question tests your understanding of monitor and maintain azure resources. 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 help desk engineer needs a Log Analytics query that returns each computer whose most recent heartbeat is older than 20 minutes. Which query should they use?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Heartbeat | summarize LastSeen = max(TimeGenerated) by Computer | where LastSeen < ago(20m)
Option B is correct because it first summarizes the most recent heartbeat timestamp for each computer using `max(TimeGenerated)`, then filters for computers where that latest heartbeat is older than 20 minutes with `where LastSeen < ago(20m)`. This ensures only computers that have not sent a heartbeat in the last 20 minutes are returned, which is the exact requirement.
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.
- ✗
Heartbeat | where TimeGenerated < ago(20m) | summarize LastSeen = max(TimeGenerated) by Computer
Why it's wrong here
This can return computers that also sent a recent heartbeat, because the newer data is filtered out before summarizing.
When this WOULD be correct
This query would be correct if the question asked: 'Which computers have had at least one heartbeat older than 20 minutes?' or 'Find computers with any heartbeat recorded more than 20 minutes ago.'
- ✓
Heartbeat | summarize LastSeen = max(TimeGenerated) by Computer | where LastSeen < ago(20m)
Why this is correct
This query first finds the latest heartbeat per computer and then filters for machines whose latest timestamp is older than 20 minutes. That matches the operational requirement exactly and avoids false positives caused by filtering before summarization.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Heartbeat | summarize count() by Computer | where count_ < 20
Why it's wrong here
Heartbeat count does not indicate when the last record was received, so a low count does not prove the computer has been silent for 20 minutes.
When this WOULD be correct
If the question asked for 'computers that have sent fewer than 20 heartbeats in total' (e.g., to identify rarely reporting machines), this query would be correct.
- ✗
Heartbeat | where TimeGenerated > ago(20m) | summarize LastSeen = max(TimeGenerated) by Computer
Why it's wrong here
This query shows machines that have had recent heartbeats, which is the opposite of the requested output.
When this WOULD be correct
If the question asked for 'computers that have sent a heartbeat in the last 20 minutes', this query would be correct because it filters to recent heartbeats and then summarizes the latest per computer.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-104 exam frequently reuses these exact scenarios with slightly different constraints.
✓Heartbeat | summarize LastSeen = max(TimeGenerated) by Computer | where LastSeen < ago(20m)Correct answer▾
Why this is correct
This query first finds the latest heartbeat per computer and then filters for machines whose latest timestamp is older than 20 minutes. That matches the operational requirement exactly and avoids false positives caused by filtering before summarization.
✗Heartbeat | where TimeGenerated < ago(20m) | summarize LastSeen = max(TimeGenerated) by ComputerWrong answer — click to see why▾
Why this is wrong here
This query filters heartbeats older than 20 minutes first, then summarizes by computer. It returns computers that have any heartbeat older than 20 minutes, even if they also have a recent heartbeat, so it does not correctly identify computers whose most recent heartbeat is older than 20 minutes.
★ When this WOULD be the correct answer
This query would be correct if the question asked: 'Which computers have had at least one heartbeat older than 20 minutes?' or 'Find computers with any heartbeat recorded more than 20 minutes ago.'
Why candidates choose this
Candidates may think filtering first and then summarizing is logically equivalent, but they overlook that the filter removes recent heartbeats, causing the summary to only consider old data, which can incorrectly include computers with recent activity.
✗Heartbeat | summarize count() by Computer | where count_ < 20Wrong answer — click to see why▾
Why this is wrong here
This query counts heartbeats per computer and filters those with fewer than 20 heartbeats, not those whose most recent heartbeat is older than 20 minutes. It does not consider the time of the last heartbeat.
★ When this WOULD be the correct answer
If the question asked for 'computers that have sent fewer than 20 heartbeats in total' (e.g., to identify rarely reporting machines), this query would be correct.
Why candidates choose this
Candidates may misinterpret 'older than 20 minutes' as 'fewer than 20 heartbeats' or mistakenly think counting events over time is equivalent to checking recency.
✗Heartbeat | where TimeGenerated > ago(20m) | summarize LastSeen = max(TimeGenerated) by ComputerWrong answer — click to see why▾
Why this is wrong here
This query filters heartbeats from the last 20 minutes and then summarizes the latest heartbeat per computer, which returns computers with heartbeats within the last 20 minutes, not those whose most recent heartbeat is older than 20 minutes.
★ When this WOULD be the correct answer
If the question asked for 'computers that have sent a heartbeat in the last 20 minutes', this query would be correct because it filters to recent heartbeats and then summarizes the latest per computer.
Why candidates choose this
Candidates may mistakenly think that filtering for recent heartbeats and then summarizing will show computers that are missing, but they overlook that the filter removes older data, so the result only includes computers with recent activity.
Analysis generated from the official AZ-104blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often filter by time first (as in Option A) thinking it will find old heartbeats, but they forget that summarizing after filtering can include computers with recent heartbeats if any old heartbeat exists, whereas the correct approach is to summarize the latest heartbeat per computer first, then filter for staleness.
Trap categories for this question
Command / output trap
This query shows machines that have had recent heartbeats, which is the opposite of the requested output.
Detailed technical explanation
How to think about this question
The `ago(20m)` function in KQL returns a datetime representing 20 minutes before the current time, and `max(TimeGenerated)` aggregates the latest timestamp per computer. This pattern is common for monitoring agent health: by summarizing first and then filtering, you avoid including computers that have both old and new heartbeats, ensuring accurate detection of stale agents. In real-world scenarios, this query is used in alert rules to trigger remediation when agents stop reporting.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
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FAQ
Questions learners often ask
What does this AZ-104 question test?
Monitor and Maintain Azure Resources — This question tests Monitor and Maintain Azure Resources — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Heartbeat | summarize LastSeen = max(TimeGenerated) by Computer | where LastSeen < ago(20m) — Option B is correct because it first summarizes the most recent heartbeat timestamp for each computer using `max(TimeGenerated)`, then filters for computers where that latest heartbeat is older than 20 minutes with `where LastSeen < ago(20m)`. This ensures only computers that have not sent a heartbeat in the last 20 minutes are returned, which is the exact requirement.
What should I do if I get this AZ-104 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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jun 11, 2026
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