The answer is that the high water mark is not being updated correctly, causing some documents to be skipped. This occurs because the Cosmos DB indexer uses the `_ts` timestamp field as a high water mark for change tracking, and the query `WHERE c._ts > @HighWaterMark` filters out any document whose timestamp is less than or equal to the last recorded high water mark value. If multiple documents share the same timestamp or if the high water mark fails to advance after a successful indexer run, those newer documents are missed during the next execution. On the Microsoft Azure AI Engineer Associate AI-102 exam, this scenario tests your understanding of incremental indexing and the pitfalls of relying solely on timestamp-based change detection, often appearing as a trick where the indexer runs without errors but still misses data. A common trap is assuming a successful run means all documents were indexed, but the high water mark mechanism can silently skip records with identical `_ts` values. Memory tip: think of the high water mark as a rising tide—if it doesn't rise, it leaves some boats stranded.
AI-102 Practice Question: Implement knowledge mining and information extraction solutions
This AI-102 practice question tests your understanding of implement knowledge mining and information extraction solutions. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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
Refer to the exhibit.
{
"$schema": "https://schemas.microsoft.com/azure/cosmosdb/2019-08-01",
"datasources": [
{
"name": "my-cosmosdb",
"type": "cosmosdb",
"credentials": { "connectionString": "AccountEndpoint=https://mycosmos.documents.azure.com:443/;AccountKey=...;" },
"container": { "name": "mycontainer", "query": "SELECT c.id, c.title, c.content FROM c WHERE c._ts > @HighWaterMark ORDER BY c._ts" }
}
]
}
You have configured an Azure AI Search indexer with a Cosmos DB data source as shown in the exhibit. The indexer runs successfully, but you notice that the index is missing some documents that were recently added to Cosmos DB. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The high water mark is not being updated correctly, causing some documents to be skipped.
The query uses '@HighWaterMark' which is a placeholder for the high water mark value used for change tracking. However, the query includes 'WHERE c._ts > @HighWaterMark' which filters out documents with a timestamp less than or equal to the high water mark. If the high water mark is not being updated correctly or if documents have the same timestamp, they might be missed. Option A is wrong because the change tracking is enabled by the query using _ts. Option B is wrong because the query selects all fields needed. Option C is wrong because the container name is correct. Option D is wrong because the connection string is valid since the indexer runs successfully.
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 indexer is not configured to track changes using _ts.
Why it's wrong here
The query uses _ts, so change tracking is enabled.
✗
The container name is misspelled.
Why it's wrong here
If misspelled, the indexer would fail.
✓
The high water mark is not being updated correctly, causing some documents to be skipped.
Why this is correct
If the high water mark is not updated, documents with _ts <= high water mark are skipped.
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.
✗
The query does not select all fields required by the index.
Why it's wrong here
Missing fields would cause indexing errors, not missing documents.
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.
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.
What to study next
Got this wrong? Here's your next step.
Identify which AI-102 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.
Implement knowledge mining and information extraction solutions — This question tests Implement knowledge mining and information extraction solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The high water mark is not being updated correctly, causing some documents to be skipped. — The query uses '@HighWaterMark' which is a placeholder for the high water mark value used for change tracking. However, the query includes 'WHERE c._ts > @HighWaterMark' which filters out documents with a timestamp less than or equal to the high water mark. If the high water mark is not being updated correctly or if documents have the same timestamp, they might be missed. Option A is wrong because the change tracking is enabled by the query using _ts. Option B is wrong because the query selects all fields needed. Option C is wrong because the container name is correct. Option D is wrong because the connection string is valid since the indexer runs successfully.
What should I do if I get this AI-102 question wrong?
Identify which AI-102 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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