SAP-C02 Continuous Improvement for Existing Solutions Practice Question
A company has an AWS Lambda function that processes files uploaded to an S3 bucket. The Lambda function has been running successfully for months. Recently, the company updated the Lambda function code and started seeing occasional throttling errors (HTTP 429) from the Lambda service. The function's reserved concurrency is set to 100. The company is unsure why throttling is occurring only after the code update. What is the MOST likely cause?
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
✓
The code update increased the execution time of the Lambda function, leading to a higher number of concurrent executions that exceed the account-level concurrency limit.
When a Lambda function's execution time increases due to a code update, each invocation holds a concurrency slot for longer. With reserved concurrency set to 100, if the function's invocations per second remain the same but each takes longer, the number of concurrent executions can exceed the account-level concurrency limit (default 1000), causing throttling (HTTP 429). Option A is wrong because CloudWatch Logs throttling would result in dropped log events, not Lambda throttling errors. Option B is wrong because if the S3 bucket received the same rate of uploads, the invocation rate wouldn't change; the question states throttling occurred only after the code update, not due to increased uploads. Option C is wrong because missing IAM permissions would cause access denied errors (HTTP 403), not throttling errors.
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 is writing logs to CloudWatch Logs at a rate that exceeds the CloudWatch throttling limit.
Why it's wrong here
CloudWatch throttling would not cause Lambda to throttle; Lambda throttling is at the invocation level.
- ✗
The S3 bucket is receiving more uploads than before, causing more Lambda invocations.
Why it's wrong here
While increased invocations could cause throttling, the question states the code update is the only change.
- ✗
The updated Lambda function no longer has the required IAM permissions to access S3, causing retries that throttle.
Why it's wrong here
Permission errors would result in 403 or 500 errors, not throttling (429).
- ✓
The code update increased the execution time of the Lambda function, leading to a higher number of concurrent executions that exceed the account-level concurrency limit.
Why this is correct
Longer execution time means more invocations overlap, increasing concurrency and potentially hitting account limits.
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.