DBS-C01 Monitoring and Troubleshooting Practice Question
A company uses Amazon DynamoDB with a table that has a partition key of 'user_id' (string) and sort key of 'timestamp' (number). The application queries for recent items for a specific user using the query API with KeyConditionExpression. The query returns items in descending order. Occasionally, the query returns items that are not the most recent. What is the most likely cause?
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
✓
The query is using eventually consistent reads, which may not reflect the latest writes.
DynamoDB queries by default use eventually consistent reads, which may not reflect the latest writes. In this scenario, the query is likely using eventually consistent reads, causing it to return stale data. Option A is correct. Option B is incorrect because ScanIndexForward set to false returns items in descending order, which is what the application expects. Option C is incorrect because pagination would result in missing items, not stale data. Option D is incorrect because the query is on the base table, not a GSI.
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 query is using eventually consistent reads, which may not reflect the latest writes.
Why this is correct
Eventually consistent reads may return stale data.
- ✗
The query is not using the ScanIndexForward parameter set to false.
Why it's wrong here
The default order is ascending; to get descending, ScanIndexForward must be set to false. But the question says it returns in descending order, so that is set correctly.
- ✗
The query results are paginated and the application is not iterating through all pages.
Why it's wrong here
Pagination would not cause incorrect order.
- ✗
The query is using a global secondary index (GSI) that has a different sort key.
Why it's wrong here
If the query uses the base table, GSI is not involved.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DBS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DBS-C01 exam.