The correct answer is to create an IAM role with a policy granting S3 access and attach it to the Lambda function. This is the best practice because it follows the principle of least privilege—the IAM role defines exactly which S3 actions and resources the Lambda function can use, and the AWS Lambda service assumes this role at runtime via a trust policy, eliminating the need for hardcoded credentials. On the AWS Certified Developer Associate DVA-C02 exam, this concept tests your understanding of service-linked roles and the shared responsibility model; a common trap is confusing Lambda execution roles with S3 bucket policies, but remember that bucket policies are for cross-account access, not for granting permissions to a Lambda function in the same account. Memory tip: “Lambda assumes, S3 allows”—the IAM role is assumed by Lambda, while the S3 bucket policy allows access from the role.
DVA-C02 Security Practice Question
This DVA-C02 practice question tests your understanding of security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 company is using AWS Lambda to process sensitive data. The Lambda function needs to access an S3 bucket in the same account. What is the BEST practice for granting permissions?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create an IAM role with a policy granting S3 access and attach it to the Lambda function.
Option A is correct because attaching an IAM role with a policy that grants S3 access to the Lambda function follows the principle of least privilege and best practice. Option B is wrong because storing secrets in environment variables is insecure. Option C is wrong because Lambda does not use key pairs. Option D is wrong because S3 bucket policies are not the primary mechanism for Lambda access; IAM roles are preferred.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use an S3 bucket policy that allows access from the Lambda function's ARN.
Why it's wrong here
Bucket policies are for cross-account access; IAM role is more appropriate.
✓
Create an IAM role with a policy granting S3 access and attach it to the Lambda function.
Why this is correct
This follows least privilege and best practice.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
Generate a key pair and use it to authenticate the Lambda function to S3.
Why it's wrong here
Key pairs are for SSH access, not for Lambda to S3.
✗
Store the AWS access key ID and secret access key in the Lambda environment variables.
Why it's wrong here
Storing credentials in environment variables is insecure.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related DVA-C02 questions on access control and AAA configuration.
Security — This question tests Security — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: Create an IAM role with a policy granting S3 access and attach it to the Lambda function. — Option A is correct because attaching an IAM role with a policy that grants S3 access to the Lambda function follows the principle of least privilege and best practice. Option B is wrong because storing secrets in environment variables is insecure. Option C is wrong because Lambda does not use key pairs. Option D is wrong because S3 bucket policies are not the primary mechanism for Lambda access; IAM roles are preferred.
What should I do if I get this DVA-C02 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related DVA-C02 questions on access control and AAA configuration.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Authentication checks who the user is.
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