The requirement is to havekey material generated and used inside a custom key store backed by an AWS CloudHSM cluster. This is exactly whatAWS KMS Custom Key Storesprovide: KMS manages the keys and policies, but the cryptographic operations for those KMS keys occur in the associatedCloudHSMcluster, keeping the key material within HSM boundaries. For applications that needlocal-use data keys(both symmetric data keys and asymmetric data key pairs), KMS supports generating data keys and data key pairs that applications can use for envelope encryption and local cryptographic operations, while the master key protections remain within KMS (and within CloudHSM when using a custom key store).
For auditing, AWS best practice isAWS CloudTrail, which records KMS API calls (such as CreateKey, GenerateDataKey, GenerateDataKeyPair, Encrypt/Decrypt, etc.) and provides an immutable event history for compliance and investigation. Athena can query logs, but it is not the primary audit record source; GuardDuty is for threat detection, not authoritative key-usage auditing. Therefore, the correct combination isKMS with a CloudHSM-backed custom key storeplusCloudTrailfor auditability.

Amazon CloudWatch Logs is designed to collect, store, and analyze log data from ephemeral compute resources such as EC2 instances in Auto Scaling groups. According to the AWS Certified Security - Specialty Study Guide, using the CloudWatch agent to stream logs off instances ensures log durability even when instances are terminated during scale-in events.
CloudWatch Logs Insights provides a fully managed, serverless query engine that enables ad hoc querying, filtering, and aggregation of log data without requiring additional infrastructure. This directly satisfies the requirement to query logs for application sessions and user troubleshooting.
Option A introduces operational risk because logs could be lost between cron executions. Option B requires additional services and data pipelines, increasing cost and complexity. Option E adds storage cost and management overhead and is not necessary for log analytics.
AWS best practices recommend CloudWatch Logs and Logs Insights as the most cost-effective and scalable solution for centralized log retention and analysis in Auto Scaling environments.
Referenced AWS Specialty Documents:
AWS Certified Security - Specialty Official Study Guide
Amazon CloudWatch Logs and Logs Insights
AWS Logging Best Practices

AWS KMS access control is primarily enforced through key policies (and optionally grants), and AWS recommends using key policy condition keys to restrict how keys can be used. The kms:ViaService condition key is specifically designed to restrict KMS API usage to requests that come through a particular AWS service endpoint in a specific Region. This is the most robust way to ensure a key can be used only via AWS Lambda (for example, lambda.<region>.amazonaws.com) and not via Amazon EC2 (ec2.<region>.
amazonaws.com), even if IAM permissions exist elsewhere. By writing a key policy that uses the Lambda execution role as the principal and conditions on kms:ViaService, the company can tightly bind key usage to Lambda-originated cryptographic operations while preventing use through EC2 service paths. Option A is weaker because EC2 is not the only way an IAM principal might use KMS, and relying on attaching explicit deny policies broadly is harder to manage and can miss principals. Option C is incorrect because aws:
AuthorizedService is not the typical mechanism for KMS service restriction, and SourceIp is unreliable for service-to-service calls. Option D is not ideal because SCPs do not provide fine-grained service-path restrictions for KMS usage and cannot "allow" beyond IAM; key policy controls still apply.
Referenced AWS Specialty Documents:
AWS Certified Security - Specialty Official Study Guide
AWS KMS Key Policies and Condition Keys
AWS KMS Best Practices for Service-Scoped Key Usage

Amazon WorkSpaces is a fully managed desktop-as-a-service solution designed to minimize infrastructure and operational overhead. According to AWS Certified Security - Specialty documentation, WorkSpaces supports device trust by using client certificates to restrict access to approved devices.
By deploying client certificates only to company-managed devices and enforcing restricted access at the directory level, the organization ensures that only trusted endpoints can authenticate. This approach avoids the cost and complexity of building and maintaining a custom VDI or managing individual EC2 instances.
Option A and B significantly increase management overhead. Option C is incorrect because IAM does not manage WorkSpaces authentication gateway policies or device trust.
AWS best practices highlight Amazon WorkSpaces with certificate-based device trust as the most efficient solution for secure, managed desktops.
Referenced AWS Specialty Documents:
AWS Certified Security - Specialty Official Study Guide
Amazon WorkSpaces Security Controls
Amazon WorkSpaces Device Trust

AWS incident response best practices emphasizecontainment with minimal blast radiuswhile preserving business continuity. According to the AWS Certified Security - Specialty Official Study Guide, isolating a compromised resource while allowing the application to continue operating is the recommended initial response.
By creating an Amazon EventBridge rule that reacts to GuardDuty anomalous traffic findings and invokes an AWS Lambda function, the security engineer can automaticallyremove the affected EC2 instance from the Auto Scaling groupand attach arestricted security group. This immediately stops malicious activity while allowing Auto Scaling to replace the instance and keep the application available.
Option A is inappropriate because EC2 instance profiles do not use long-term access keys. Option C applies subnet-wide changes that could disrupt unrelated workloads. Option D provides notification only and does not meet the automated response requirement.
AWS documentation explicitly identifiesinstance isolation via security groupsas a preferred containment technique that preserves application availability and forensic integrity.
* AWS Certified Security - Specialty Official Study Guide
* Amazon GuardDuty User Guide
* AWS Incident Response Best Practices