SAP-C02 Design for New Solutions Practice Question
A company is designing a new serverless application using AWS Lambda. The function must process a file uploaded to S3 and then send a notification to an external API. The external API has a rate limit of 10 requests per second. Which approach should they use to handle throttling?
⚠ Common exam trap
Test-takers frequently choose SNS fan-out (Option D) thinking it improves throughput, but they fail to recognize that it amplifies concurrency and worsens throttling, whereas SQS with reserved concurrency provides controlled, decoupled processing.
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
✓
Use Amazon SQS to buffer the requests and set a Lambda reserved concurrency to limit the processing rate
Amazon SQS acts as a durable buffer that decouples the S3 event from the Lambda invocation, allowing the function to poll messages at a controlled rate. By setting a Lambda reserved concurrency, you limit the number of concurrent executions, which directly caps the processing rate to stay within the external API's 10 requests per second limit. This combination ensures that the Lambda function does not exceed the API's throttling threshold while still processing all events reliably.
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 Amazon SQS to buffer the requests and set a Lambda reserved concurrency to limit the processing rate
Why this is correct
SQS can buffer requests and Lambda reserved concurrency can limit concurrency, effectively throttling the rate.
- ✗
Increase the Lambda function timeout and retry on failure
Why it's wrong here
Increasing timeout does not control the rate of API calls.
- ✗
Configure a Lambda function destination on failure to reprocess
Why it's wrong here
This only handles failures, not rate control.
- ✗
Use Amazon SNS to fan out the notification to multiple Lambda functions
Why it's wrong here
SNS does not provide rate limiting.
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 by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAP-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 SAP-C02 exam.