DVA-C02 Troubleshooting and Optimization Practice Question
A developer is troubleshooting an AWS Lambda function that is timing out. The function processes S3 events and writes to DynamoDB. The average execution time is 5 seconds, but the function times out after 3 seconds. What is the most likely cause?
⚠ Common exam trap
DVA-C02 often tests the confusion between a function timing out due to its own configured timeout versus downstream service throttling — candidates see 'DynamoDB' in the stem and jump to capacity, ignoring that the timeout value (3s) exactly matches the default and is below the stated 5s runtime.
Answer choices
Why each option matters
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 timeout is set to 3 seconds.
The function's average execution time is 5 seconds, but it times out at 3 seconds — this mismatch directly indicates the Lambda function's configured timeout value is set to 3 seconds, which is lower than the actual runtime. The timeout setting is a per-function configuration (default 3 seconds, max 15 minutes) that terminates execution when exceeded. Since the workload legitimately needs ~5 seconds, the fix is to increase the timeout to a value above the observed runtime.
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 S3 bucket is not configured to send event notifications.
Why it's wrong here
If an S3 bucket is not configured to send event notifications, the Lambda function would simply not be invoked in response to S3 events. This scenario would prevent the function from starting at all, rather than causing it to execute and then time out. A timeout error specifically indicates that the function began execution but failed to complete its processing within its allotted time limit.
- ✗
DynamoDB write capacity is insufficient.
Why it's wrong here
Insufficient write capacity in DynamoDB leads to throttling of write requests, resulting in ProvisionedThroughputExceededException errors or increased latency as the AWS SDK retries operations. While these delays could potentially contribute to a Lambda function exceeding its timeout if the function is already near its limit, the direct effect is a failed or delayed database operation, not an inherent timeout of the Lambda runtime itself. The Lambda function would still be actively executing, waiting for the DynamoDB call to complete.
- ✓
The Lambda function timeout is set to 3 seconds.
Why this is correct
The Lambda function timeout configuration directly dictates the maximum duration an invocation is allowed to run before the Lambda service forcibly terminates it. If the function's code, including any synchronous downstream calls or complex processing, requires more than 3 seconds to complete, it will inevitably result in a timeout error. The default timeout is often 3 seconds, and increasing this value is the primary solution when a function consistently fails to finish within its allocated execution window.
- ✗
The Lambda function concurrency limit is exceeded.
Why it's wrong here
Exceeding a Lambda function's concurrency limit causes the Lambda service to throttle new invocation requests, rejecting them with a TooManyRequestsException (HTTP 429) before the function even begins execution. This prevents the function from starting, meaning it cannot run long enough to experience a timeout during its execution. A timeout occurs when an already running function exceeds its configured maximum execution duration.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
This DVA-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 DVA-C02 exam.