AWS Certified Solutions Architect – Professional (SAP-C02) — Question 508

A company is using AWS to develop and manage its production web application. The application includes an Amazon API Gateway HTTP API that invokes an AWS Lambda function. The Lambda function processes and then stores data in a database.

The company wants to implement user authorization for the web application in an integrated way. The company already uses a third-party identity provider that issues OAuth tokens for the company’s other applications.

Which solution will meet these requirements?

Answer options

• A. Integrate the company’s third-party identity provider with API Gateway. Configure an API Gateway Lambda authorizer to validate tokens from the identity provider. Require the Lambda authorizer on all API routes. Update the web application to get tokens from the identity provider and include the tokens in the Authorization header when calling the API Gateway HTTP API.
• B. Integrate the company's third-party identity provider with AWS Directory Service. Configure Directory Service as an API Gateway authorizer to validate tokens from the identity provider. Require the Directory Service authorizer on all API routes. Configure AWS IAM Identity Center as a SAML 2.0 identity Provider. Configure the web application as a custom SAML 2.0 application.
• C. Integrate the company’s third-party identity provider with AWS IAM Identity Center. Configure API Gateway to use IAM Identity Center for zero-configuration authentication and authorization. Update the web application to retrieve AWS Security Token Service (AWS STS) tokens from IAM Identity Center and include the tokens in the Authorization header when calling the API Gateway HTTP API.
• D. Integrate the company’s third-party identity provider with AWS IAM Identity Center. Configure IAM users with permissions to call the API Gateway HTTP API. Update the web application to extract request parameters from the IAM users and include the parameters in the Authorization header when calling the API Gateway HTTP API.

Correct answer: A

Explanation

An Amazon API Gateway Lambda authorizer is the standard way to validate custom OAuth tokens issued by a third-party identity provider. By requiring this authorizer on the HTTP API routes and passing the tokens in the Authorization header from the client application, the system achieves secure, integrated validation. Other options incorrectly attempt to leverage AWS Directory Service or AWS IAM Identity Center for direct API Gateway token validation, which do not support this use case natively.