The correct answer is that the function code expects a property that is missing from the event payload. This Lambda runtime error, specifically "Cannot read property of undefined," occurs when your code attempts to access a property—like 'length' or 'name'—on an object that does not exist in the event object passed during invocation. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of how Lambda processes incoming events and the importance of validating payload structure before accessing nested properties. A common trap is confusing this error with a timeout or permission issue, but the logs clearly show the function started and ran, ruling out those causes. The key is to inspect the event object shape and ensure your code handles missing keys gracefully. Memory tip: think "Check the payload, not the policy"—if the property is undefined, the problem is in the data, not the permissions.
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.
Network Topology
A developer invoked a Lambda function and saw the above output. What is the root cause of the error?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The function code expects a property that is missing from the event payload.
Option C is correct because the error message 'Cannot read property 'length' of undefined' suggests that the code expects a property that does not exist in the event object. Option A is wrong because there is no timeout error. Option B is wrong because the log shows the function started and ran. Option D is wrong because there is no mention of missing permissions.
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 lacks permission to access the event payload.
Why it's wrong here
Permissions affect access to AWS resources, not event data.
✓
The function code expects a property that is missing from the event payload.
Why this is correct
The code tries to access 'length' on undefined, meaning expected property not in event.
Related concept
Read the scenario before looking for a memorised answer.
✗
The Lambda function's handler name is incorrect.
Why it's wrong here
The function started executing, so handler is correct.
✗
The Lambda function timed out.
Why it's wrong here
No timeout error; function ran and threw an exception.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 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.
Identify which DVA-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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 function code expects a property that is missing from the event payload. — Option C is correct because the error message 'Cannot read property 'length' of undefined' suggests that the code expects a property that does not exist in the event object. Option A is wrong because there is no timeout error. Option B is wrong because the log shows the function started and ran. Option D is wrong because there is no mention of missing permissions.
What should I do if I get this DVA-C02 question wrong?
Identify which DVA-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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