DBS-C01 Global Secondary Index (GSI) ARN Practice Question
A company uses Amazon DynamoDB with fine-grained access control using IAM policies. A developer reports that an application role can read and write to the 'orders' table but cannot perform a Scan operation on a Global Secondary Index (GSI). The IAM policy attached to the role includes 'dynamodb:Scan' and the resource ARN for the table. What is the likely reason for this failure?
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 IAM policy does not include the GSI's ARN in the resource statement.
DynamoDB Global Secondary Indexes (GSIs) have their own Amazon Resource Names (ARNs) separate from the base table. When using IAM policies with fine-grained access control, the policy must explicitly include the ARN of the GSI in the resource statement to allow operations like Scan on that GSI. Without the GSI ARN, the Scan operation on the GSI is denied by default, even if the policy allows 'dynamodb:Scan' on the base table. Option A is incorrect because the policy does not mention time-of-day conditions. Option B is incorrect because the role can read from the base table, but the issue is with the GSI. Option D is incorrect because the action 'dynamodb:Scan' is allowed on the table but not on the 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 policy has a condition that restricts Scan operations based on the time of day.
Why it's wrong here
This is unlikely because the scenario does not mention any condition keys restricting Scan by time of day; the issue is resource ARN mismatch.
- ✗
The role does not have permission to read from the base table.
Why it's wrong here
This is incorrect because the role has permission to read and write to the base table, so it does have read access to the base table.
- ✓
The IAM policy does not include the GSI's ARN in the resource statement.
Why this is correct
This is correct because GSIs have separate ARNs in DynamoDB. The policy must explicitly include the GSI ARN to allow operations like Scan on that index.
- ✗
The IAM policy does not allow the 'dynamodb:Scan' action on the table.
Why it's wrong here
This is incorrect because the policy does include 'dynamodb:Scan' on the table ARN, so the action is allowed on the table; the failure is due to the GSI not being covered.
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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.