The answer is that the Lambda function is not reusing database connections properly, exhausting the proxy connection pool. When the RDS Proxy’s DatabaseConnections metric is consistently at its maximum of 1000, every new Lambda invocation must wait for a free connection, causing increased latency and eventual timeouts as the pool saturates. This tests your understanding of connection management in serverless architectures on the AWS Certified Developer Associate DVA-C02 exam—a common trap is assuming that RDS Proxy alone prevents exhaustion, but it only pools connections; the Lambda code must still reuse them across invocations via techniques like connection pooling or keeping connections alive in the execution environment. Remember the key insight: RDS Proxy manages the database connections, but your Lambda code must manage the proxy connections. Memory tip: “Pool full = code dull”—if the pool is full, your code isn’t reusing connections.
DVA-C02 Troubleshooting and Optimization Practice Question
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 notices that an AWS Lambda function, which uses Amazon RDS Proxy to connect to an Aurora MySQL database, is experiencing increased latency and occasional connection timeouts. The function is configured with a reserved concurrency of 100 and is deployed in a VPC. The RDS Proxy's maximum connections is set to 1000. CloudWatch metrics show that the DatabaseConnections metric for the proxy is consistently at 1000. What is the most likely cause of the increased latency and timeouts?
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 Lambda function is not reusing database connections properly, exhausting the proxy connection pool
The RDS Proxy's DatabaseConnections metric is consistently at 1000, which equals the proxy's maximum connections setting. This indicates the proxy connection pool is fully saturated. When all connections are in use, new connection requests from Lambda invocations must wait, causing increased latency, and if the wait exceeds the timeout, connection timeouts occur. The most likely cause is that the Lambda function is not reusing database connections (e.g., not using connection pooling or keeping connections open across invocations), exhausting the pool.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 Lambda function is not reusing database connections properly, exhausting the proxy connection pool
Why this is correct
Correct. Each invocation opens a new connection without reuse, causing the proxy to reach its connection limit.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The RDS Proxy target group is not configured with the correct DB instance
Why it's wrong here
If misconfigured, connections would fail immediately, not cause gradual exhaustion.
✗
The Lambda function's execution role is missing the rds-db:connect permission
Why it's wrong here
Missing permissions would result in consistent connection failures, not gradual latency increase.
✗
The VPC does not have a NAT Gateway for outbound traffic
Why it's wrong here
NATGateway is needed for internet access, not for connecting to RDS Proxy within the same VPC.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may focus on the reserved concurrency (100) versus proxy max connections (1000) and assume the numbers are fine, missing that the real issue is connection reuse per invocation, not the total count.
Detailed technical explanation
How to think about this question
RDS Proxy maintains a connection pool to the database, reusing connections across multiple Lambda invocations. If the Lambda function creates a new database connection on every invocation without closing or reusing it (e.g., not using a connection pool library like mysql2/promise with keep-alive), each invocation consumes a proxy connection. With reserved concurrency of 100, even 10 concurrent invocations each opening 10 connections could saturate the 1000-connection pool, leading to queueing and timeouts. Under the hood, RDS Proxy uses multiplexing but still enforces a hard limit on the number of client connections.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The Lambda function is not reusing database connections properly, exhausting the proxy connection pool — The RDS Proxy's DatabaseConnections metric is consistently at 1000, which equals the proxy's maximum connections setting. This indicates the proxy connection pool is fully saturated. When all connections are in use, new connection requests from Lambda invocations must wait, causing increased latency, and if the wait exceeds the timeout, connection timeouts occur. The most likely cause is that the Lambda function is not reusing database connections (e.g., not using connection pooling or keeping connections open across invocations), exhausting the pool.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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Question Discussion
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