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AWS WAF (Web Application Firewall): AWS WAF allows you to create custom rules to block or allow web requests based on conditions that you specify.

Web ACL (Access Control List):

Create a web ACL and associate it with the ALB.

Use IP rule sets to specify the IP addresses of the retail locations that are allowed to access the application.

Security and Flexibility:

AWS WAF provides a scalable way to manage access control, ensuring that only traffic from registered IP addresses is allowed.

You can dynamically update the IP rule sets to add or remove IP addresses as needed.

Operational Simplicity: Using AWS WAF with a web ACL is straightforward and integrates seamlessly with the ALB, providing an efficient solution for managing access control based on IP addresses.

Amazon S3 Object Lock is the AWS feature designed for WORM storage. AWS documentation says Object Lock helps prevent objects from being deleted or overwritten for a fixed amount of time or indefinitely and supports a WORM model. In compliance mode, even an administrator cannot shorten or remove the retention period before it expires, which is critical for confidential medical records and regulatory retention. Setting a 1-year retention period satisfies the minimum retention requirement, and IAM policies can still control which approved users are allowed to upload new objects. MFA Delete and ordinary IAM policies do not provide the same immutable WORM guarantees. A custom Lambda-based approach would add unnecessary complexity and still would not be the native compliance-oriented control that S3 Object Lock provides.

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The correct answer isCbecause the company needs asecure cross-account accesssolution that usestemporary credentials, followsleast privilege, and avoidslong-term access keys. The best practice for this design is to allow anIAM role in Account Ato access theAmazon S3 bucket in Account Bthrough aresource-based bucket policy. Analysts or applications in Account A can assume the IAM role and receive temporary credentials through AWS Security Token Service (AWS STS), which satisfies the requirement to avoid permanent access keys.

This approach is secure because permissions can be scoped precisely to the required bucket and prefixes, supporting least-privilege access. It also avoids creating separate IAM users in Account B and eliminates the operational and security risks of sharing static credentials across accounts. Cross-account access through IAM roles and S3 bucket policies is the standard AWS pattern for securely granting one account access to resources in another account.

Option A is incorrect because creating IAM users and sharing access keys introduces long-term credentials, which the company explicitly wants to avoid. Option B is incorrect because making the S3 bucket public violates security requirements and does not enforce least privilege. Option D is incorrect because using a bastion host adds unnecessary infrastructure and operational overhead and is not the recommended approach for S3 access.

AWS security best practices favorrole-based access with temporary credentialsandresource policiesfor cross-account resource sharing. Therefore, configuring the S3 bucket policy in Account B to allow access from an IAM role in Account A is the most secure and appropriate solution.

This solution offers the least operational overhead while meeting the security and global availability requirements:

Amazon CloudFront and S3: Hosting the static frontend on S3 and serving it via CloudFront provides low-latency global distribution, high availability, and security. S3 is a cost-effective and serverless option for hosting static assets, and CloudFront ensures that the application is cached closer to the users, reducing latency globally.

AWS Lambda and API Gateway: Refactoring the microservices to use Lambda functions with API Gateway allows for a fully serverless, scalable, and highly available backend. This reduces the need for managing EC2 instances, as Lambda automatically scales to meet demand and only charges for the actual usage.

RDS for MySQL: Migrating the MySQL database from an EC2 instance to Amazon RDS significantly reduces operational overhead. RDS manages backups, patching, and scaling, and it offers high availability options (e.g., Multi-AZ).

Option AandDinvolve using EC2 Reserved Instances for the database, which requires more operational maintenance than using RDS.

Option Csuggests using a Network Load Balancer with Lambda, which adds unnecessary complexity for this use case.

AWS References:

Amazon S3 and CloudFront Integration

AWS Lambda with API Gateway

Amazon RDS for MySQL