The answer is to configure S3 event notifications to filter by prefix and suffix and to use a DynamoDB table to track processed file IDs. These two measures ensure idempotent Lambda processing of S3 files by preventing duplicate invocations at the source and enabling the function to skip already-processed objects. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of event-driven architectures and the common failure mode where S3 event notifications can fire multiple times for the same upload, especially with large files or retries. A frequent trap is assuming that increasing the Lambda timeout or adding SQS alone solves duplication—SQS requires explicit deduplication logic, while S3 filters directly reduce event noise. Memory tip: think “filter first, then check”—use S3 prefix/suffix filters to limit triggers, and DynamoDB as a persistent idempotency token to catch any stragglers.
SAP-C02 Continuous Improvement for Existing Solutions Practice Question
This SAP-C02 practice question tests your understanding of continuous improvement for existing solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 company is using an AWS Lambda function to process files uploaded to an S3 bucket. The function is written in Python and uses the boto3 library to read the files. Recently, some files have been processed multiple times. Which TWO measures should a solutions architect implement to ensure idempotent processing?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a DynamoDB table to store processed file IDs and check for duplicates before processing.
Options B and D are correct. Using a DynamoDB table to track processed file IDs (B) allows the function to skip duplicates. Enabling S3 event notifications with a prefix and suffix filter (D) reduces the chance of multiple events for the same object. Option A is wrong because increasing Lambda timeout doesn't prevent multiple invocations. Option C is wrong because SQS can help but needs deduplication logic as well. Option E is wrong because S3 Transfer Acceleration is for faster uploads, not idempotency.
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.
✓
Use a DynamoDB table to store processed file IDs and check for duplicates before processing.
Why this is correct
Idempotency key store prevents duplicate processing.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure the S3 bucket to send events to an SQS queue and use the Lambda function to poll the queue.
Why it's wrong here
SQS helps with scaling but still needs deduplication logic.
✗
Increase the Lambda function timeout to 15 minutes.
Why it's wrong here
Timeout does not prevent duplicate processing.
✓
Configure S3 event notifications to filter by prefix and suffix to avoid triggering multiple times.
Why this is correct
Filtering reduces unnecessary invocations.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable S3 Transfer Acceleration on the bucket.
Why it's wrong here
Transfer Acceleration improves upload speed, not idempotency.
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 SAP-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.
Continuous Improvement for Existing Solutions — This question tests Continuous Improvement for Existing Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a DynamoDB table to store processed file IDs and check for duplicates before processing. — Options B and D are correct. Using a DynamoDB table to track processed file IDs (B) allows the function to skip duplicates. Enabling S3 event notifications with a prefix and suffix filter (D) reduces the chance of multiple events for the same object. Option A is wrong because increasing Lambda timeout doesn't prevent multiple invocations. Option C is wrong because SQS can help but needs deduplication logic as well. Option E is wrong because S3 Transfer Acceleration is for faster uploads, not idempotency.
What should I do if I get this SAP-C02 question wrong?
Identify which SAP-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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