The answer is to configure the Lambda function for VPC access and use a VPC endpoint for S3. This combination is the most secure because it allows the Lambda function to reach the VPC-hosted database for enrichment while keeping all S3 traffic within the AWS network, never traversing the public internet. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of how to build a secure serverless pipeline that balances private resource access with cost efficiency—a common trap is choosing a NAT Gateway, which adds unnecessary expense and attack surface, or an Internet Gateway, which exposes the function. Remember the key principle: Lambda in a VPC loses default internet access, so you must use a VPC endpoint for S3 to avoid routing data through a NAT. Memory tip: “Lambda in the VPC, S3 via endpoint—no NAT, no internet, just secure.”
SAP-C02 Design for New Solutions Practice Question
This SAP-C02 practice question tests your understanding of design for new solutions. 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 building a serverless data processing pipeline. Data is uploaded to an S3 bucket, which triggers a Lambda function to transform the data and store the result in another S3 bucket. The Lambda function needs to access a VPC-hosted database for enrichment. What is the MOST secure way to allow the Lambda function to access the VPC resources?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the Lambda function to access the VPC and use a VPC endpoint for S3.
Configuring Lambda to access a VPC (option C) allows it to reach VPC resources while using a VPC endpoint for S3 (option D) keeps S3 traffic within AWS network. Option A (NATGateway) is less secure and adds cost. Option B (Internet Gateway) exposes the function. Option C with option D is best.
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.
✗
Assign a public IP to the Lambda function and route through an Internet Gateway.
Why it's wrong here
Public IP exposure is unnecessary and insecure.
✓
Configure the Lambda function to access the VPC and use a VPC endpoint for S3.
Use Lambda@Edge to process data at the edge location.
Why it's wrong here
Lambda@Edge is for CloudFront events, not for VPC access.
✗
Place the Lambda function in a public subnet and use a NAT Gateway.
Why it's wrong here
Public subnet and NATGateway are less secure and add complexity.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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 SAP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Design for New Solutions — This question tests Design for New Solutions — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Configure the Lambda function to access the VPC and use a VPC endpoint for S3. — Configuring Lambda to access a VPC (option C) allows it to reach VPC resources while using a VPC endpoint for S3 (option D) keeps S3 traffic within AWS network. Option A (NAT Gateway) is less secure and adds cost. Option B (Internet Gateway) exposes the function. Option C with option D is best.
What should I do if I get this SAP-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 SAP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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