Quick Answer
The answer is that the S3 bucket's event notification still points to the old Lambda function. This is the most likely cause because S3 event notifications are configured with a specific Lambda function ARN, and when you deploy a new version without updating that ARN—or without using an alias or the $LATEST qualifier—events continue routing to the previous version, which may be inactive or not logging, explaining why CloudWatch Logs show no errors. On the AWS Certified Developer Associate DVA-C02 exam, this tests your understanding of how S3 event notifications are static ARN references, not dynamic pointers to the latest code; a common trap is assuming that redeploying a function automatically updates the trigger. Remember the memory tip: "S3 notifications are stuck on the old ARN—update the trigger, not just the code."
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 deployed a new version of a Lambda function that processes S3 events. After deployment, some S3 events are not being processed. The CloudWatch Logs show no errors. What 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.
The Lambda function has a syntax error.
Why wrong: No errors in logs.
The S3 bucket's event notification still points to the old Lambda function.
S3 event notification must be updated to invoke the new function.
The Lambda function alias is not pointing to the new version.
Why wrong: S3 invokes the function, not an alias.
The S3 events are being throttled by Lambda.
Why wrong: Throttling would produce errors in logs.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The S3 bucket's event notification still points to the old Lambda function.
Option B is correct because after deploying a new version of a Lambda function, the S3 bucket's event notification configuration still references the Amazon Resource Name (ARN) of the old Lambda function version or the function without a qualifier. S3 event notifications are configured to invoke a specific Lambda function ARN, and if the ARN does not point to the new version (e.g., by using an alias or the $LATEST qualifier), events will continue to be sent to the old version, which may not be processing them. Since CloudWatch Logs show no errors, the old version is likely not being invoked or is not logging, confirming the mismatch.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The Lambda function has a syntax error.
Why it's wrong here
No errors in logs.
The S3 bucket's event notification still points to the old Lambda function.
Why this is correct
S3 event notification must be updated to invoke the new function.
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 Lambda function alias is not pointing to the new version.
Why it's wrong here
S3 invokes the function, not an alias.
The S3 events are being throttled by Lambda.
Why it's wrong here
Throttling would produce errors in logs.
Common exam traps
The trap here is that candidates assume deploying a new Lambda version automatically updates all event sources, but S3 event notifications are static ARN references that must be manually updated or use aliases to reflect the new version.
Detailed technical explanation
S3 event notifications use a resource-based policy to grant S3 permission to invoke the Lambda function. When you deploy a new version, the function ARN changes (e.g., arn:aws:lambda:region:account:function:myFunction:1 vs :2). If the notification is hardcoded to version 1, events go to that version. Using an alias (e.g., 'prod') allows you to update the alias to point to the new version without modifying the S3 notification. Under the hood, Lambda invokes the function version specified in the event source mapping; if no version is specified, it defaults to $LATEST, which may not be the deployed version if you published a new one.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Read the scenario before looking for a memorised answer..
The correct answer is: The S3 bucket's event notification still points to the old Lambda function. — Option B is correct because after deploying a new version of a Lambda function, the S3 bucket's event notification configuration still references the Amazon Resource Name (ARN) of the old Lambda function version or the function without a qualifier. S3 event notifications are configured to invoke a specific Lambda function ARN, and if the ARN does not point to the new version (e.g., by using an alias or the $LATEST qualifier), events will continue to be sent to the old version, which may not be processing them. Since CloudWatch Logs show no errors, the old version is likely not being invoked or is not logging, confirming the mismatch.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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