A function URL is a dedicated HTTP(S) endpoint for your Lambda function. When you create a function URL, Lambda automatically generates a unique URL endpoint for you.

Keyword "Lambda function" and "webhook". See https://docs.aws.amazon.com/eventbridge/latest/userguide/eb-saas-furls.html#create-stripe-cfn-stack

AWS Lambda can provide a URL to call using Function URLs. This is a relatively new feature in AWS Lambda that allows you to create HTTPS endpoints for your Lambda functions, making it easy to invoke the function directly over the web. Key Features of Lambda Function URLs: Direct Access: Provides a simple and direct way to call a Lambda function via an HTTP(S) request. Easy Configuration: You can create a function URL for a Lambda function using the AWS Management Console, AWS CLI, or AWS SDKs. Managed Service: AWS manages the infrastructure for you, handling scaling, patching, and maintenance. Security: You can configure authentication and authorization using AWS IAM or AWS Lambda function URL settings.

Apart from simplest and most operational, I think A is the only option that will work! BCD cannot even be implemented in real world imho. Happy to be corrected

B is the answerThe best solution to make the Lambda function available for the third party to call with the MOST operational efficiency is to deploy an Application Load Balancer (ALB) in front of the Lambda function and provide the ALB URL to the third party for the webhook. This solution is the most efficient because it allows the third party to call the Lambda function without having to worry about managing the Lambda function's availability or scaling. The ALB will automatically distribute traffic across multiple Lambda functions, if necessary, and will also provide redundancy in case of a failure.

The key points: A Lambda function needs to be invoked by a third party via a webhook. Using a function URL provides a direct invoke endpoint for the Lambda function. This is simple and efficient. Options B, C, and D insert unnecessary components like ALB, SNS, SQS between the webhook and the Lambda function. These add complexity without benefit. A function URL can be generated and provided to the third party quickly without additional infrastructure.

key word: Lambda function URLs

https://docs.aws.amazon.com/lambda/latest/dg/lambda-urls.html

It's A

A would seem like the correct one but not sure.