DVA-C02 Development with AWS Services Practice Question
This DVA-C02 practice question tests your understanding of development with aws services. 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 building an application that processes user-uploaded images. The application uses Amazon S3 to store the images and AWS Lambda to generate thumbnails. When a user uploads an image to an S3 bucket, an S3 event notification triggers a Lambda function. The Lambda function processes the image and saves the thumbnail to another S3 bucket. The developer notices that sometimes the Lambda function is not triggered after an upload. The developer checks the Lambda function's CloudWatch logs and sees no invocation records for those uploads. The S3 bucket event notification configuration appears correct. What is the most likely cause of this issue?
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 S3 bucket and the Lambda function are in different AWS regions.
Option A is correct because S3 event notifications might not be delivered if the bucket is in a different region than the Lambda function; the Lambda function must be in the same region as the S3 bucket for S3 event notifications. Option B is wrong because the Lambda function's IAM role does not affect invocation; it affects execution. Option C is wrong because S3 event notifications are not asynchronous; they are delivered synchronously. Option D is wrong because the destination bucket's permissions are not relevant to the invocation trigger.
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.
✗
The destination S3 bucket does not have the correct bucket policy to allow the Lambda function to write thumbnails.
Why it's wrong here
This would cause the Lambda function to fail during execution, not prevent invocation.
✗
The S3 event notification is configured as an asynchronous invocation, and the event is lost.
Why it's wrong here
S3 event notifications are synchronous; they invoke Lambda directly.
✗
The Lambda function's execution role does not have permission to read from the S3 bucket.
Why it's wrong here
The execution role is used for the Lambda function to access resources, not for S3 to invoke Lambda.
✓
The S3 bucket and the Lambda function are in different AWS regions.
Why this is correct
S3 event notifications can only trigger Lambda functions in the same region.
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.
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.
Development with AWS Services — This question tests Development with AWS Services — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The S3 bucket and the Lambda function are in different AWS regions. — Option A is correct because S3 event notifications might not be delivered if the bucket is in a different region than the Lambda function; the Lambda function must be in the same region as the S3 bucket for S3 event notifications. Option B is wrong because the Lambda function's IAM role does not affect invocation; it affects execution. Option C is wrong because S3 event notifications are not asynchronous; they are delivered synchronously. Option D is wrong because the destination bucket's permissions are not relevant to the invocation trigger.
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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