AWS Certified Solutions Architect – Professional (SAP-C02) — Question 497

A company creates an Amazon API Gateway API and shares the API with an external development team. The API uses AWS Lambda functions and is deployed to a stage that is named Production.

The external development team is the sole consumer of the API. The API experiences sudden increases of usage at specific times, leading to concerns about increased costs. The company needs to limit cost and usage without reworking the Lambda functions.

Which solution will meet these requirements MOST cost-effectively?

Answer options

• A. Configure the API to send requests to Amazon Simple Queue Service (Amazon SQS) queues instead of directly to the Lambda functions. Update the Lambda functions to consume messages from the queues and to process the requests. Set up the queues to invoke the Lambda functions when new messages arrive.
• B. Configure provisioned concurrency for each Lambda function. Use AWS Application Auto Scaling to register the Lambda functions as targets. Set up scaling schedules to increase and decrease capacity to match changes in API usage.
• C. Create an API Gateway API key and an AWS WAF Regional web ACL. Associate the web ACL with the Production stage. Add a rate-based rule to the web ACL. In the rule, specify the rate limit and a custom request aggregation that uses the X-API-Key header. Share the API key with the external development team.
• D. Create an API Gateway API Key and usage plan. Define throttling limits and quotas in the usage plan. Associate the usage plan with the Production stage and the API key. Share the API key with the external development team.

Correct answer: D

Explanation

Option D is correct because API Gateway usage plans allow administrators to define throttling limits and quotas directly at the API stage level without modifying backend Lambda code, which directly restricts usage and controls costs. Option A requires modifying the backend architecture to use Amazon SQS, which does not directly limit overall usage. Option B introduces provisioned concurrency which increases costs, and Option C introduces the unnecessary additional expense of AWS WAF when native API Gateway usage plans can meet the requirement.