DVA-C02 Development with AWS Services Practice Question
This DVA-C02 practice question tests your understanding of development with aws services. 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 deploying an application on Amazon ECS using the Fargate launch type. The application needs to communicate with a DynamoDB table. The developer creates a VPC with private subnets and configures the ECS service to use those subnets. However, the tasks cannot reach DynamoDB. 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 VPC does not have a VPC endpoint for DynamoDB, and there is no NAT gateway.
Option B is correct because private subnets need a VPC endpoint (or NATgateway) to access DynamoDB. Option A is wrong because security groups control traffic at instance level, but the issue is routing. Option C is wrong because IAM roles are for permissions, not network connectivity. Option D is wrong because task definitions don't have network settings for VPC endpoints.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 task IAM role does not have permissions to access DynamoDB.
Why it's wrong here
Incorrect: Permissions are separate from network connectivity.
✗
The security group of the tasks does not allow outbound traffic to DynamoDB.
Why it's wrong here
Incorrect: Security groups are stateful; outbound is allowed by default.
✓
The VPC does not have a VPC endpoint for DynamoDB, and there is no NAT gateway.
Why this is correct
Correct: Private subnets cannot reach DynamoDB without a VPC endpoint or NAT.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The task definition does not have a network mode that supports DynamoDB.
Why it's wrong here
Incorrect: Network mode does not affect access to DynamoDB.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DVA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Development with AWS Services — This question tests Development with AWS Services — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The VPC does not have a VPC endpoint for DynamoDB, and there is no NAT gateway. — Option B is correct because private subnets need a VPC endpoint (or NAT gateway) to access DynamoDB. Option A is wrong because security groups control traffic at instance level, but the issue is routing. Option C is wrong because IAM roles are for permissions, not network connectivity. Option D is wrong because task definitions don't have network settings for VPC endpoints.
What should I do if I get this DVA-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DVA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
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?
CIDR notation defines the prefix length.
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