AWS Certified Solutions Architect – Professional (SAP-C02) — Question 290

A company is creating a REST API to share information with six of its partners based in the United States. The company has created an Amazon API Gateway Regional endpoint. Each of the six partners will access the API once per day to post daily sales figures.

After initial deployment, the company observes 1,000 requests per second originating from 500 different IP addresses around the world. The company believes this traffic is originating from a botnet and wants to secure its API while minimizing cost.

Which approach should the company take to secure its API?

Answer options

• A. Create an Amazon CloudFront distribution with the API as the origin. Create an AWS WAF web ACL with a rule to block clients that submit more than five requests per day. Associate the web ACL with the CloudFront distribution. Configure CloudFront with an origin access identity (OAI) and associate it with the distribution. Configure API Gateway to ensure only the OAI can run the POST method.
• B. Create an Amazon CloudFront distribution with the API as the origin. Create an AWS WAF web ACL with a rule to block clients that submit more than five requests per day. Associate the web ACL with the CloudFront distribution. Add a custom header to the CloudFront distribution populated with an API key. Configure the API to require an API key on the POST method.
• C. Create an AWS WAF web ACL with a rule to allow access to the IP addresses used by the six partners. Associate the web ACL with the API. Create a resource policy with a request limit and associate it with the API. Configure the API to require an API key on the POST method.
• D. Create an AWS WAF web ACL with a rule to allow access to the IP addresses used by the six partners. Associate the web ACL with the API. Create a usage plan with a request limit and associate it with the API. Create an API key and add it to the usage plan.

Correct answer: D

Explanation

Associating an AWS WAF web ACL directly with the Regional API Gateway endpoint allows the company to allowlist the known IP addresses of the six partners, blocking the unauthorized botnet traffic at the source. Implementing an API Gateway usage plan combined with an API key provides a low-cost, built-in mechanism to enforce request limits and throttle traffic. Options A and B introduce unnecessary costs and complexity by using CloudFront, and OAIs are designed for Amazon S3, not API Gateway. Option C is incorrect because resource policies do not support request limiting; usage plans must be used for this purpose.