The answer is to configure the Lambda function to access the VPC and place it in the same subnets as the RDS instance. This is correct because when you enable VPC access for a Lambda function, AWS creates an elastic network interface (ENI) in those subnets, allowing the function to communicate directly with the RDS database over private IP addresses without traversing the public internet. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of how to securely connect serverless compute to private databases, often appearing as a distractor where candidates mistakenly choose VPC endpoints or a Network Load Balancer. The key trap is that VPC endpoints only work for AWS services like S3 or DynamoDB, not for RDS instances, and a public internet connection is not an option here. Remember the memory tip: "Lambda lives in the VPC, not through a gateway" — if the database is inside the VPC, your Lambda must join the same subnets to reach it.
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 designing a new serverless application using AWS Lambda. The Lambda function needs to access an Amazon RDS database. The database is in a VPC without public internet access. What is the MOST secure way to allow the Lambda function to connect to the database?
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 place it in the same subnets as the RDS instance.
Option B is correct because configuring the Lambda function to access the VPC allows it to use an ENI to connect to the RDS instance within the VPC. Option A is wrong because the database is not publicly accessible. Option C is wrong because VPC endpoints are for accessing AWS services, not RDS instances. Option D is wrong because Network Load Balancer is not needed for direct database connections.
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.
✓
Configure the Lambda function to access the VPC, and place it in the same subnets as the RDS instance.
Why this is correct
Lambda can connect to resources in a VPC via an Elastic Network Interface (ENI) in the same subnets.
Create a VPC endpoint for Amazon RDS and use it from Lambda.
Why it's wrong here
VPC endpoints are for accessing AWS services like S3 or DynamoDB, not RDS instances.
✗
Use an AWS Network Load Balancer in front of the RDS instance and connect Lambda to the NLB.
Why it's wrong here
NLB is not designed for database access; it adds unnecessary complexity and latency.
✗
Create a public endpoint for the RDS instance and allow Lambda to connect over the internet.
Why it's wrong here
This exposes the database to the internet, which is insecure and against requirements.
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 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 place it in the same subnets as the RDS instance. — Option B is correct because configuring the Lambda function to access the VPC allows it to use an ENI to connect to the RDS instance within the VPC. Option A is wrong because the database is not publicly accessible. Option C is wrong because VPC endpoints are for accessing AWS services, not RDS instances. Option D is wrong because Network Load Balancer is not needed for direct database connections.
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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is designing a serverless application using AWS Lambda. The function needs to access a VPC resource. What is the correct way to configure this?
medium
A.Attach an Internet Gateway to the VPC
✓ B.Assign the Lambda function to the VPC and configure a security group
C.Set up a VPC peering connection
D.Configure a NAT Gateway in the public subnet
Why B: Lambda functions must be attached to a VPC and assigned a security group to access resources within the VPC, such as an RDS database or an Elasticache cluster. This configuration creates an elastic network interface (ENI) in the VPC, allowing the function to communicate with VPC resources via private IP addresses. The security group acts as a virtual firewall to control inbound and outbound traffic for the Lambda function.
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This SAP-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAP-C02 exam.
Question Discussion
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