The answer is to check that the Lambda function has a route to the database via a NAT gateway or VPC endpoint. When a Lambda function is VPC-enabled, it loses default internet access and can only reach resources within its VPC; to connect to an RDS database that resides in a private subnet, the function must have a route through a NAT gateway for public endpoints or a VPC endpoint for private connectivity. This scenario tests your understanding of Lambda’s VPC networking model, a core concept on the AWS Certified Solutions Architect Professional SAP-C02 exam, where the common trap is assuming security groups or NACLs are the root cause when the real issue is missing outbound routing. The search intent for Lambda VPC configuration timeout connecting to RDS database often catches candidates who overlook that a VPC-enabled Lambda cannot reach resources outside its subnet without explicit routing. Remember the mnemonic: “Lambda in a VPC needs a path to flee” — without a NAT or endpoint, it’s trapped.
SAP-C02 Continuous Improvement for Existing Solutions Practice Question
This SAP-C02 practice question tests your understanding of continuous improvement for existing 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 uses AWS Lambda with a VPC configuration to access an RDS database. After a recent change, the Lambda function times out when connecting to the database. The security group and network ACLs appear correct. What should the company check first?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
That the Lambda function has a route to the database via a NAT gateway or VPC endpoint.
When a Lambda function is VPC-enabled, it requires a VPC endpoint for services like S3, DynamoDB, or a NATgateway for internet access. If the function needs to access the database via a public endpoint, a NAT gateway is needed. Option D is correct. Option A is about Lambda's environment variables. Option B is about database credentials. Option C is about Lambda's concurrency, not connectivity.
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.
✗
That the database password has not been rotated.
Why it's wrong here
Password rotation would cause authentication errors, not timeouts.
✗
That the Lambda function's reserved concurrency is not set to zero.
Why it's wrong here
Reserved concurrency would cause throttling, not timeouts.
✓
That the Lambda function has a route to the database via a NAT gateway or VPC endpoint.
Why this is correct
If the database is in a private subnet, a NATgateway is needed for the Lambda function to access it.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
That the Lambda function's environment variables are correctly set.
Why it's wrong here
Environment variables affect configuration, not network connectivity.
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 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 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.
Continuous Improvement for Existing Solutions — This question tests Continuous Improvement for Existing Solutions — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: That the Lambda function has a route to the database via a NAT gateway or VPC endpoint. — When a Lambda function is VPC-enabled, it requires a VPC endpoint for services like S3, DynamoDB, or a NAT gateway for internet access. If the function needs to access the database via a public endpoint, a NAT gateway is needed. Option D is correct. Option A is about Lambda's environment variables. Option B is about database credentials. Option C is about Lambda's concurrency, not connectivity.
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: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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