Amazon RDS for MySQL Reserved Instances provide significant savings over on-demand pricing when you plan to run the database for long periods. This is the most cost-effective option for non-production, long- running managed MySQL workloads.
Reference Extract:
"Reserved Instances provide a significant discount compared to On-Demand pricing and are recommended for steady-state workloads that run for an extended period." Source: AWS Certified Solutions Architect - Official Study Guide, RDS Cost Optimization section.

* The requirement to "have access to the operating system" means the compute layer must be Amazon EC2 (or containers on EC2). Managed runtimes such as Lambda and Fargate do not provide OS-level access.
* The requirement for a "low-latency NoSQL database" maps directly to Amazon DynamoDB, which is a fully managed NoSQL key-value and document database that provides single-digit millisecond latency at any scale.
* Because the application runs in a private subnet, AWS best practice is to access DynamoDB privately via a VPC endpoint (gateway endpoint for DynamoDB). This avoids traversing the public internet and simplifies security.
* An instance profile (EC2 role) is the recommended method to grant EC2 instances permission to access DynamoDB without hardcoding credentials.
Why the other options are not correct:
* B: Lambda does not provide OS access, which violates the security requirement.
* C: Fargate does not provide OS access, and Aurora PostgreSQL is a relational database, not NoSQL.
* D: S3 + Athena is an analytics pattern, not a low-latency NoSQL database solution; query latency is much higher and not suitable for OLTP-style app storage.

* Storage Gateway Volume Gateway (Cached Volumes): This configuration allows you to store your primary data in Amazon S3 while retaining frequently accessed data locally in a cache for low-latency access.
* Low-Latency Access: Frequently accessed data is cached locally on-premises, providing low-latency access while the less frequently accessed data is stored cost-effectively in Amazon S3.
* Implementation:
* Deploy a Storage Gateway appliance on-premises or in a virtual environment.
* Configure it as a volume gateway with cached volumes.
* Create volumes and configure your applications to use these volumes.
* Minimal Infrastructure Changes: This solution integrates seamlessly with existing on-premises infrastructure, requiring minimal changes and reducing dependency on on-premises storage servers.
References:
* AWS Storage Gateway Volume Gateway
* Volume Gateway Cached Volumes

The correct answer isBbecause the company needs tocentrally manage backups across multiple AWS accounts, improvedisaster recovery posture, and protect backups fromaccidental deletion or compromise of an AWS account.AWS Backup policies in AWS Organizationsprovide centralized governance and automation for backup plans across member accounts. By storing copies of backups inadditional AWS accounts, the company gains stronger isolation and protection against account-level compromise.
Cross-account backup copies are especially important when the requirement includes protection from a malicious attack on an AWS account. If backups remain only in the same account, an attacker with sufficient permissions in that account could potentially alter or delete them. Storing backup copies in a separate account provides administrative separation and strengthens recovery options. This is a recognized AWS best practice for improving cyber resilience and recovery assurance.
Option A is incorrect because copying backups to additional Availability Zones within the same account does not address centralized management across Organizations or protect against malicious actions in that account.
Option C improves regional resilience but still lacks centralized policy-based management and account isolation. Option D provides centralized policy management and cross-Region resilience, but it does not directly address the requirement to protect against an attack on a single AWS account as effectively ascross- account backup copies.
AWS guidance for enterprise backup strategy emphasizescentralized backup management with AWS Backup and AWS Organizations, pluscross-account copiesfor stronger protection and recovery. Therefore, usingAWS Backup policies in Organizations to store copies in additional AWS accountsis the best solution.

* A. Fixed desired instances: Does not adapt to traffic load fluctuations, leading to inefficiencies.
* B. Larger EC2 instances: Increases costs unnecessarily.
* C. Target tracking scaling policy: Adjusts capacity based on actual demand, optimizing costs.
* D. Instance store volumes: Not persistent and unsuitable for shared data across instances.
References: Auto Scaling