The answer is to use an Amazon VPC interface endpoint for Lambda while keeping the function outside the VPC. This configuration minimizes Lambda cold start latency because placing a function inside a VPC requires creating an elastic network interface (ENI) during initialization, which adds several seconds of delay; by using a VPC interface endpoint, the function remains outside the VPC yet can still securely access the database through the endpoint, avoiding that ENI creation overhead entirely. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of Lambda’s VPC networking trade-offs—specifically that VPC-enabled functions incur cold start penalties, while interface endpoints decouple access from placement. A common trap is assuming Lambda must live inside the VPC to reach private resources, but the correct approach is to keep it outside and connect via an endpoint. Memory tip: “Outside, endpoint inside—no ENI, no delay.”
SAP-C02 Design for New Solutions Practice Question
This SAP-C02 practice question tests your understanding of design for new solutions. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 serverless application using AWS Lambda that processes images uploaded to an S3 bucket. The processing time varies but typically completes within 5 minutes. The Lambda function needs to access a VPC-hosted database. What is the BEST way to configure the Lambda function to access the database while minimizing cold start latency?
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
✓
Use an Amazon VPC interface endpoint for Lambda and keep the function outside the VPC
Option B is correct because using a VPC interface endpoint for Lambda avoids placing the function inside the VPC, which eliminates cold start latency due to ENI creation. Option A is incorrect because placing Lambda in the VPC adds cold start delays. Option C is incorrect because RDS Proxy does not eliminate the need for VPC access. Option D is incorrect because a NATgateway is for outbound internet, not inbound database access.
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.
✗
Place the Lambda function outside the VPC and use a NAT gateway to reach the database
Why it's wrong here
NATgateway is for outbound traffic; the database is inbound.
✗
Place the Lambda function inside the VPC with a security group allowing access to the database
Why it's wrong here
Lambda in VPC requires ENI creation, increasing cold start latency.
✗
Use Amazon RDS Proxy to manage connections and keep Lambda outside the VPC
Why it's wrong here
RDS Proxy requires the Lambda function to be in the VPC or use a VPC endpoint.
✓
Use an Amazon VPC interface endpoint for Lambda and keep the function outside the VPC
Why this is correct
Interface endpoints allow VPC access without placing Lambda in the VPC, reducing cold starts.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
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 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 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 SAP-C02 NAT questions on configuration and troubleshooting.
Design for New Solutions — This question tests Design for New Solutions — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Use an Amazon VPC interface endpoint for Lambda and keep the function outside the VPC — Option B is correct because using a VPC interface endpoint for Lambda avoids placing the function inside the VPC, which eliminates cold start latency due to ENI creation. Option A is incorrect because placing Lambda in the VPC adds cold start delays. Option C is incorrect because RDS Proxy does not eliminate the need for VPC access. Option D is incorrect because a NAT gateway is for outbound internet, not inbound database access.
What should I do if I get this SAP-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 SAP-C02 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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