The answer is that the IAM policy does not include the `dynamodb:DescribeTable` action. This is the most likely reason for the failure because IAM permissions are explicit allow-by-default; the policy only grants `GetItem` and `PutItem`, so any action not listed, such as `DescribeTable`, is implicitly denied. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of least-privilege IAM policies and the specific actions required for DynamoDB operations. A common trap is assuming that broad resource access (`"Resource": "*"`) or read/write actions automatically include metadata operations like `DescribeTable`, but they do not. Remember the memory tip: "Describe is not Get or Put" — metadata actions must be explicitly allowed alongside data-plane actions.
DBS-C01 Database Security Practice Question
This DBS-C01 practice question tests your understanding of database security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 developer is troubleshooting an issue where an IAM user cannot perform a 'DescribeTable' action on a DynamoDB table. The IAM policy attached to the user is: {"Version":"2012-10-17","Statement":[{"Effect":"Allow","Action":["dynamodb:GetItem","dynamodb:PutItem"],"Resource":"*"}]}. What is the most likely reason for the failure?
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 policy does not include the 'dynamodb:DescribeTable' action.
Option B is correct because the policy only allows GetItem and PutItem, not DescribeTable. Option A is wrong because the resource is '*' which covers all tables. Option C is wrong because DynamoDB actions are case-sensitive, but the policy uses correct casing. Option D is wrong because there is no explicit Deny in the policy.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 uses lowercase 'dynamodb' but the action is case-sensitive.
Why it's wrong here
The service prefix is lowercase and actions are PascalCase; 'dynamodb:GetItem' is correct.
✗
There is an implicit Deny for DescribeTable due to a service control policy.
Why it's wrong here
No SCP mentioned; the policy itself lacks the action.
✓
The policy does not include the 'dynamodb:DescribeTable' action.
Why this is correct
The policy only allows GetItem and PutItem.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The resource specified in the policy is '*' which does not include the table.
Why it's wrong here
'*' does include all tables.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DBS-C01 ACL questions on filtering logic and placement.
Database Security — This question tests Database Security — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The policy does not include the 'dynamodb:DescribeTable' action. — Option B is correct because the policy only allows GetItem and PutItem, not DescribeTable. Option A is wrong because the resource is '*' which covers all tables. Option C is wrong because DynamoDB actions are case-sensitive, but the policy uses correct casing. Option D is wrong because there is no explicit Deny in the policy.
What should I do if I get this DBS-C01 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DBS-C01 ACL questions on filtering logic and placement.
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?
Standard ACLs match source addresses.
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