You are developing a REST API in Amazon API Gateway. The API integrates with a Lambda Function. You found that when clients hit the API using an unsupported method, the API Gateway has returned a Missing Authentication Token (403) response. As the response does not provide much information, you want to customize the response. For example, you want to change the error code to 404 and add some custom HTTP headers. How would you implement this?

Answer options:

A.In the AWS API Gateway console, choose Gateway Responses under the API and select the 403 response. Add custom headers and modify the response status code to 404.
B.In the API method`s integration response, add the custom headers and modify the status code to 404.
C.In the AWS API Gateway console, select the Missing Authentication Token 403 response. Forward it to an HTTP 404 Not Found response. Select the 404 response and add custom headers accordingly.
D.Select the API method and click the integration response. Forward the 403 response to a 404 Not Found response. In the meantime, add the custom headers in the forwarded response.

Correct Answer – A
Users can customize the gateway response using the API Gateway console according to 
https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-gateway-response-using-the-console.html.
Option A is CORRECT: Users can select the particular Missing Authentication Token 403 gateway response under the API and customize it as below screenshot:
Option B is incorrect: In this scenario, it needs to modify the default gateway response. The integration response of the API method should not be changed.
Option C is incorrect: Because in the AWS API Gateway console, users cannot forward a gateway response to another. Instead, the status code, headers and bodies should be customized.
Option D is incorrect: Similar to option
B. The method configuration should not be modified. It does not change the API Gateway behavior when clients hit an unsupported method.