Deploying the shared libraries and custom classes to a Docker image and uploading the image to Amazon Elastic Container Registry (Amazon ECR) and creating a Lambda layer that uses the Docker image as the source. Then, deploying the API's Lambda functions as Zip packages and configuring the packages to use the Lambda layer would meet the requirements for simplifying the deployment and optimizing for code reuse.
A Lambda layer is a distribution mechanism for libraries, custom runtimes, and other function dependencies.
It allows you to manage your in-development function code separately from your dependencies, this way you can easily update your dependencies without having to update your entire function code.
By deploying the shared libraries and custom classes to a Docker image and uploading the image to Amazon Elastic Container Registry (ECR), it makes it easy to manage and version the dependencies. This way, the company can use the same version of the dependencies across different Lambda functions.
By creating a Lambda layer that uses the Docker image as the source, the company can configure the API's Lambda functions to use the layer, reducing the need to include the dependencies in each function package, and making it easy to update the dependencies across all functions at once.
Reference:
AWS Lambda Layers documentation:https://docs.aws.amazon.com/lambda/latest/dg/configuration-layers.html AWS Elastic Container Registry (ECR) documentation:https://aws.amazon.com/ecr/ Building Lambda Layers with Docker documentation:https://aws.amazon.com/blogs/compute/building- lambda-layers-with-docker/

Comprehensive and Detailed Explanation:
C is correct because:
* AWS WAF integrates natively with API Gateway and protects against common web exploits (e.g., SQL injection, XSS).
* Amazon Inspector can scan the legacy EC2 instance for known vulnerabilities.
* Amazon GuardDuty is a continuous security monitoring service that detects threats butdoes not block traffic (B and D are incorrect because GuardDuty doesn't block).
References:
AWS WAF Overview
Amazon Inspector Overview
Amazon GuardDuty Overview

* Identify Proxy EC2 Instances:
* Determine which EC2 instances in the private subnets are running the proxy server software.
* Disable Source/Destination Checks:
* For each of these EC2 instances, go to the AWS Management Console.
* Navigate to the EC2 dashboard, select the instance, and choose "Actions" > "Networking" >
"Change Source/Dest. Check".
* Disable the source/destination check for these instances.
Disabling source/destination checks allows the EC2 instances to route traffic appropriately, enabling them to function as network appliances or proxies. This ensures that traffic from other instances in the private subnets can be routed through the proxy instances to the internet, meeting the company's security requirements.
References
* Amazon EC2 User Guide on Source/Destination Checks

This option uses AWS DataSync to replicate the on-premises images to the EFS file system over the Direct Connect connection. AWS DataSync is a service that automates and accelerates data transfer between on-premises storage systems and AWS storage services. It can transfer data to and from Amazon EFS, Amazon FSx for Windows File Server, and Amazon S3. To use AWS DataSync, the company needs to deploy an AWS DataSync agent to an on-premises server that has access to the NFS file system. The agent connects to the AWS DataSync service endpoint in the AWS Region where the EFS file system is located. The company can use an AWS PrivateLink interface endpoint to connect to the service endpoint securely and privately over the Direct Connect connection. The company can then create a task in AWS DataSync that specifies the source location (the NFS file system), the destination location (the EFS file system), and the options for the data transfer (such as schedule, bandwidth limit, and verification). AWS DataSync will then perform the data transfer efficiently and securely, using encryption in transit and at rest.

https://medium.com/@it.melnichenko/invoke-a-lambda-across-multiple-aws-accounts-8c094b2e70be