AWS Certified Solutions Architect – Professional (SAP-C02) — Question 117

A company is building a software-as-a-service (SaaS) solution on AWS. The company has deployed an Amazon API Gateway REST API with AWS Lambda integration in multiple AWS Regions and in the same production account.

The company offers tiered pricing that gives customers the ability to pay for the capacity to make a certain number of API calls per second. The premium tier offers up to 3,000 calls per second, and customers are identified by a unique API key. Several premium tier customers in various Regions report that they receive error responses of 429 Too Many Requests from multiple API methods during peak usage hours. Logs indicate that the Lambda function is never invoked.

What could be the cause of the error messages for these customers?

Answer options

• A. The Lambda function reached its concurrency limit.
• B. The Lambda function its Region limit for concurrency.
• C. The company reached its API Gateway account limit for calls per second.
• D. The company reached its API Gateway default per-method limit for calls per second.

Correct answer: C

Explanation

The correct answer is C because the 429 Too Many Requests error indicates that the overall API Gateway account limit for calls per second has been exceeded. The Lambda function not being invoked suggests that the issue is related to the API Gateway limits rather than the Lambda concurrency limits, making options A and B incorrect. Option D is also not the right answer as it refers to per-method limits, while the problem is with the overall account limit.