The answer is that the EC2 instance is not using the VPC endpoint to access DynamoDB; it is instead routing traffic through an internet gateway. This is the most likely cause because the IAM policy condition specifically requires the request to originate from the VPC endpoint, but if the instance’s route table does not direct DynamoDB traffic to the endpoint, the request will leave the VPC via the internet gateway, bypassing the endpoint entirely. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of how VPC endpoint conditions interact with network routing—a common trap is assuming that simply being in the same VPC is enough. Remember, the condition checks the source of the request, not the subnet or instance location. A helpful memory tip: “If it doesn’t hit the endpoint, the condition won’t bend.”
SCS-C02 Identity and Access Management Practice Question
This SCS-C02 practice question tests your understanding of identity and access management. 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.
An IAM policy grants access to a DynamoDB table with a condition that the request must originate from a specific VPC endpoint. However, requests from an EC2 instance in that VPC are being denied. 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 EC2 instance is not using the VPC endpoint to access DynamoDB; it is using an internet gateway.
Option A is correct because the EC2 instance needs to have a route to the VPC endpoint; if not, traffic goes through the internet and doesn't use the endpoint. Option B is wrong because the instance does not need a public IP. Option C is wrong because the endpoint policy must allow the action. Option D is wrong because security groups control network traffic, not IAM conditions.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 EC2 instance does not have a public IP address.
Why it's wrong here
Public IP is not required for VPC endpoint access.
✗
The security group on the EC2 instance does not allow outbound traffic to the DynamoDB endpoint.
Why it's wrong here
Security groups control network traffic, but the condition is about VPC endpoint source.
✓
The EC2 instance is not using the VPC endpoint to access DynamoDB; it is using an internet gateway.
Why this is correct
The condition requires the request to come through the VPC endpoint; if the instance routes traffic via internet, the condition fails.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The VPC endpoint policy does not allow the specific DynamoDB action.
Why it's wrong here
While possible, the question implies the policy is correct; the most likely cause is routing.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SCS-C02 NAT questions on configuration and troubleshooting.
Identity and Access Management — This question tests Identity and Access Management — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The EC2 instance is not using the VPC endpoint to access DynamoDB; it is using an internet gateway. — Option A is correct because the EC2 instance needs to have a route to the VPC endpoint; if not, traffic goes through the internet and doesn't use the endpoint. Option B is wrong because the instance does not need a public IP. Option C is wrong because the endpoint policy must allow the action. Option D is wrong because security groups control network traffic, not IAM conditions.
What should I do if I get this SCS-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SCS-C02 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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