The answer is S3 GET request throttling during high traffic, as this is the most likely cause of sporadic Lambda timeouts when reading from an S3 bucket. When multiple concurrent invocations of the Lambda function issue GET requests against the same S3 prefix, you can exceed the bucket’s 5,500 GET/HEAD request-per-second-per-prefix limit, causing S3 to throttle those requests with a 503 SlowDown response. This throttling introduces unpredictable delays that manifest as intermittent timeouts, unlike cold starts which only affect the first invocation, or memory exhaustion which typically causes outright failures rather than timeouts. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of S3 performance limits and how they interact with Lambda concurrency—a common trap is confusing throttling with cold starts or VPC misconfigurations. Remember the memory tip: “S3 throttles GETs under high concurrency, not cold starts or memory.”
DVA-C02 Troubleshooting and Optimization Practice Question
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 is troubleshooting a Lambda function that times out sporadically. The function reads from an S3 bucket and processes CSV files. Which of the following is the MOST likely cause?
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
✓
S3 GET request throttling during high traffic.
Sporadic timeouts often occur due to throttling or limits. S3 throttling (especially for GET requests) can cause delays. Cold starts would cause initial delays but not sporadic ones. Memory exhaustion would cause failures, not timeouts. VPC configuration would cause consistent timeouts.
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.
✗
VPC configuration missing a NAT gateway.
Why it's wrong here
Missing NATgateway would cause consistent connectivity issues, not sporadic timeouts.
✗
Cold starts due to low invocation frequency.
Why it's wrong here
Cold starts cause initial delays but not sporadic timeouts during steady state.
✓
S3 GET request throttling during high traffic.
Why this is correct
High request rates can lead to S3 throttling, causing intermittent delays and timeouts.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
Insufficient memory allocated to the Lambda function.
Why it's wrong here
Insufficient memory usually causes out-of-memory errors, not timeouts.
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 DVA-C02 NAT questions on configuration and troubleshooting.
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: S3 GET request throttling during high traffic. — Sporadic timeouts often occur due to throttling or limits. S3 throttling (especially for GET requests) can cause delays. Cold starts would cause initial delays but not sporadic ones. Memory exhaustion would cause failures, not timeouts. VPC configuration would cause consistent timeouts.
What should I do if I get this DVA-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 DVA-C02 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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