Question 274 of 1,170

Monitor and Maintain Azure Resources →mediumMultiple ChoiceObjective-mapped

Quick Answer

The correct query is `Heartbeat | summarize LastSeen = max(TimeGenerated) by Computer | where LastSeen < ago(20m)`. This works because it first groups all heartbeat records by each computer, then uses the `max(TimeGenerated)` function to capture the single most recent timestamp for that machine, and finally applies a filter with `ago(20m)` to keep only those computers whose latest heartbeat falls outside the 20-minute window. On the AZ-104 exam, this tests your ability to combine aggregation with time-based filtering in KQL—a common scenario for monitoring agent health and identifying stale endpoints. A frequent trap is forgetting to use `summarize` before filtering, which would return individual stale records rather than the computer-level status. Remember the pattern: summarize first to get the latest, then filter with `ago()` to find the missing. A handy mnemonic is “Summarize the max, then filter the gap”—it reinforces that you must collapse the data before applying the time condition.

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?

Question 1mediummultiple choice

Full question →

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.

Full breakdown with real-world context →

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.
✓
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.
✗
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.

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

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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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.

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Same concept, more angles

1 more ways this is tested on AZ-104

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A help desk analyst needs a KQL query that identifies each VM's most recent heartbeat so computers can be flagged if their last check-in is older than 20 minutes. Which two KQL elements should be used? Select two.

medium

✓ A.Query the Heartbeat table, because it stores the heartbeat records for Azure VMs.
✓ B.Summarize max(TimeGenerated) by Computer to get the most recent heartbeat per VM.
C.Join the results to AzureActivity to calculate service health.
D.Filter where TimeGenerated is older than 20 minutes before summarizing.
E.Use the Perf table because it stores heartbeat timestamps.

Why A: Option A is correct because the Heartbeat table in Azure Monitor Logs (Log Analytics) is specifically designed to store heartbeat records from Azure Monitor Agent (AMA) or the legacy Log Analytics agent. Each heartbeat record contains a TimeGenerated timestamp, making it the authoritative source for determining when a VM last reported its health status.

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