The answer is that the Lambda function’s IAM role lacks a permissions policy allowing CloudWatch Logs actions. This is the most likely cause because the Lambda runtime requires explicit permissions to create log groups and log streams and to put log events—specifically the `logs:CreateLogGroup`, `logs:CreateLogStream`, and `logs:PutLogEvents` actions. Without these, any attempt to write logs results in an access denied error at invocation. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of Lambda execution roles and the principle of least privilege; a common trap is assuming the Lambda service itself handles logging automatically, or confusing the trust policy with the permissions policy. Remember that the role must grant logging permissions, not just trust the Lambda service. A helpful memory tip: think “Create, Create, Put” for the three required log actions—without them, your logs are stuck in the void.
DVA-C02 Security Practice Question
This DVA-C02 practice question tests your understanding of 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.
Network Topology
Refer to the exhibit. A developer created an IAM role for a Lambda function. When the Lambda function invokes, it fails with an access denied error when trying to write logs to CloudWatch Logs. 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 role lacks a permissions policy that allows CloudWatch Logs actions.
Option C is correct because the Lambda function's IAM role must include a permissions policy that grants the `logs:CreateLogGroup`, `logs:CreateLogStream`, and `logs:PutLogEvents` actions. Without these permissions, the Lambda runtime cannot write logs to CloudWatch Logs, resulting in an access denied error. The error occurs at invocation time when the Lambda service attempts to create or write to the log stream on behalf of the function.
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 trust policy does not allow the Lambda service to assume the role.
Why it's wrong here
The trust policy allows Lambda to assume the role.
✗
The CloudWatch Logs log group has a resource-based policy that denies the Lambda function.
Why it's wrong here
The issue is the role's permissions, not the log group policy.
✓
The role lacks a permissions policy that allows CloudWatch Logs actions.
Why this is correct
Without a permissions policy, the role cannot perform any actions.
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 Lambda function is not associated with this role.
Why it's wrong here
If the function is associated, it can assume the role.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse trust policies with permissions policies, assuming that if the role is assumed successfully, all subsequent API calls will work, but the trust policy only governs role assumption, not the actions the role can perform.
Detailed technical explanation
How to think about this question
Under the hood, the Lambda execution environment uses the IAM role's credentials to make AWS API calls. The CloudWatch Logs agent in the Lambda runtime calls `CreateLogGroup`, `CreateLogStream`, and `PutLogEvents` sequentially; if any of these actions are denied by an IAM permissions policy, the entire log write fails. A real-world scenario is when developers attach a managed policy like `AWSLambdaBasicExecutionRole` but then inadvertently remove or override it with a custom policy that lacks the `logs:` actions, causing silent log failures.
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.
TExam Day Tips
→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 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The role lacks a permissions policy that allows CloudWatch Logs actions. — Option C is correct because the Lambda function's IAM role must include a permissions policy that grants the `logs:CreateLogGroup`, `logs:CreateLogStream`, and `logs:PutLogEvents` actions. Without these permissions, the Lambda runtime cannot write logs to CloudWatch Logs, resulting in an access denied error. The error occurs at invocation time when the Lambda service attempts to create or write to the log stream on behalf of the function.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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