DBS-C01 Workload-Specific Database Design Practice Question
Exhibit
Refer to the exhibit.
IAM policy document (CloudFormation snippet):
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": [
"dynamodb:GetItem",
"dynamodb:Query",
"dynamodb:Scan"
],
"Resource": "arn:aws:dynamodb:us-east-1:123456789012:table/mytable",
"Condition": {
"ForAllValues:StringEquals": {
"dynamodb:LeadingKeys": ["user_${aws:userid}"]
}
}
}
]
}A company uses the IAM policy shown in the exhibit to control access to a DynamoDB table. The table has a partition key user_id and a sort key timestamp. The application uses the AWS SDK to query items. When a user tries to query items with a filter condition, they receive an AccessDeniedException. What is the most likely cause?
⚠ Common exam trap
The trap here is that candidates may overlook the `LeadingKeys` condition and assume the error is due to a missing action or a policy syntax issue, rather than recognizing that the query must include a partition key matching the condition value.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The query does not specify a partition key that matches the user's LeadingKeys condition.
The IAM policy uses a `Condition` block with `ForAllValues:StringEquals` on `dynamodb:LeadingKeys` to restrict access to items where the partition key (`user_id`) matches the caller's IAM user ID (`${aws:userid}`). When a query does not specify a partition key that satisfies this condition, the request fails with an `AccessDeniedException`. The error occurs because the query must include a partition key equal to the user's ID to pass the leading keys restriction.
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 aws:userid variable is not being resolved correctly.
Why it's wrong here
The variable is correctly resolved in IAM policies.
- ✓
The query does not specify a partition key that matches the user's LeadingKeys condition.
Why this is correct
The condition restricts access to items with a partition key equal to the user's ID; if the query does not use that partition key, access is denied.
- ✗
The policy is missing a Condition element with dynamodb:Select.
Why it's wrong here
No such condition is needed.
- ✗
The policy does not allow the Query action.
Why it's wrong here
The policy allows Query, so that is not the issue.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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