To resolve DNS across VPCs in different accounts, you should:

Authorization: In Account B, initiate a VPC association authorization for the private hosted zone. This

action allows another AWS account to associate a VPC with this hosted zone.

Association: In Account A, after receiving the authorization from Account B, associate its VPC with

the private hosted zone that exists in Account B. This step will enable EC2 instances within the VPC in

Account A to resolve DNS records hosted in Account B.

AWS Documentation Reference:

AWS provides detailed guidance on associating VPCs with private hosted zones across accounts in

their documentation: Associating VPCs and Private Hosted Zones Across Accounts.

Aurora Auto Scaling:

Aurora Auto Scaling adjusts the number of Aurora Replicas in response to changes in connectivity or

workload.

Steps:

Go to the AWS Management Console.

Navigate to RDS and select the Aurora cluster.

Under "Actions," choose "Add Aurora Replica" to initially add replicas if needed.

Go to the "Auto Scaling" section and create an auto scaling policy.

Set the target value for the DatabaseConnections metric to 195.

Define the minimum and maximum number of replicas.

Save the configuration.

This ensures that the Aurora cluster scales automatically when the number of connections

approaches the threshold, improving read performance.

Aurora Auto Scaling

AWS Systems Manager Run Command provides an efficient method to execute administrative tasks

on EC2 instances. This solution will minimize the time and complexity involved:

Select Document: Choose AWS-RunShellScript for Linux-based instances or AWS-

RunPowerShellScript for Windows-based instances.

Configure Command: Enter the mitigation script provided by the security team into the command

document.

Target Instances: Use the tagging system to target only the instances that match the specific OS as

identified by their tags.

Execute Command: Run the command across the targeted instances.

Verification and Reporting: The command history in Systems Manager will serve as evidence of

execution and success, which can be reported back to the security team.

AWS Documentation Reference:

More about Run Command can be found here: AWS Systems Manager Run Command.

This solution is operationally efficient and leverages AWS services to provide notifications when the

Lambda function is not invoked, indicating that the file did not arrive.

Steps:

Create a CloudWatch Alarm:

Open the Amazon CloudWatch console.

In the navigation pane, choose "Alarms" and then "Create Alarm".

Select Lambda Metrics:

Choose "Select metric" and then navigate to "AWS Lambda" metrics.

Select the Lambda function that processes the S3 files.

Choose the "Invocations" metric.

Configure the Alarm:

Set the period to 1 hour.

Define the threshold condition to trigger when the Invocations metric is zero.

Under "Additional configuration", configure the alarm to treat missing data as "breaching".

Set Alarm Actions:

Configure the alarm action to send a notification to an Amazon SNS topic.

Create an SNS topic if one does not exist, and subscribe the application team to this topic.

Testing and Verification:

Ensure that the alarm triggers correctly by simulating a missing file scenario and confirming that the

notification is sent to the SNS topic.

This approach uses CloudWatch to monitor the invocation frequency of the Lambda function,

ensuring that the application team is notified whenever the expected file does not arrive within the

specified timeframe.

Reference:

Amazon CloudWatch Alarms

Monitoring Lambda Functions

Amazon SNS Notifications

When using the RequestCountPerTarget metric for scaling in an Auto Scaling group, the behavior of

instance scaling follows specific rules set by Auto Scaling policies and cooldown periods:

Scaling Trigger: The Auto Scaling group triggers a scaling action whenever the

RequestCountPerTarget exceeds the predefined limit set in the scaling policy.

Cooldown Period: After launching an EC2 instance due to a scaling action, the Auto Scaling group

enters a cooldown period. During this period, despite further breaches of the threshold, no

additional instances will be launched. This is designed to give the newly launched instance time to

start and begin handling traffic, preventing the Auto Scaling group from launching too many

instances too quickly.

This mechanism helps maintain efficient use of resources by adapting to changes in load while

avoiding rapid, unnecessary scaling actions.

AWS CloudFormation StackSets extends the functionality of stacks by enabling you to create, update,

or delete stacks across multiple accounts and regions with a single operation. Using a stack set, the

SysOps administrator can manage deployments across different regions and accounts within AWS

Organizations efficiently.

Setting up StackSets: First, define your CloudFormation template that describes all the resources that

need to be deployed across the regions. Store this template in an S3 bucket accessible by the central

administration account.

Service-Managed Permissions: When creating a stack set, select the option for service-managed

permissions if you are using AWS Organizations. This allows AWS CloudFormation to automatically

set up the necessary permissions in the target accounts.

Deploying the Stack Set: From the central administration account, create the stack set and specify the

target accounts and regions. CloudFormation will then ensure that the resources defined in the

template are instantiated in each of the specified regions and accounts.

This method simplifies management and ensures consistency of infrastructure across multiple

regions and accounts, leveraging the organizational units in AWS Organizations for centralized

governance.

AWS Backup supports automated backups for EC2 (including attached EBS volumes). It allows:

Central management

Scheduled daily backups

Low operational overhead

From AWS Backup documentation:

You can create backup plans with schedules and retention rules, and assign resources like EC2

instances for automated backup.

CloudTrail Log File Integrity Validation:

AWS CloudTrail provides a feature for log file integrity validation to ensure logs have not been

modified or deleted.

Steps to Enable and Validate:

Enable Log File Integrity Validation:

Go to the CloudTrail Console.

Select or create a trail.

In the trail settings, enable Log file validation.

Use the AWS CLI for Validation:

Use the following CLI command:

aws cloudtrail validate-logs --trail-name

This command validates the digest files generated by CloudTrail against the log files.

Why Other Options Are Incorrect:

B: Using the AWS CloudTrail Processing Library is unnecessary for validation.

C: CloudTrail Insights is designed to identify unusual activity, not monitor log modifications.

D: Amazon CloudWatch Logs cannot directly monitor CloudTrail logs for integrity.

Reference:

CloudTrail Log File Validation

AWS CLI Command for Validation

To ensure that the Auto Scaling group scales out when CPU utilization rises above 50%, the

administrator should configure the Auto Scaling group to dynamically scale based on demand. This is

achieved by setting up a scaling policy that triggers based on specific CloudWatch alarms—like CPU

utilization exceeding 50%. This dynamic scaling method directly responds to changes in workload,

ensuring that resources are allocated efficiently and promptly as demand increases. Option C is the

correct answer, aligning with best practices for managing EC2 Auto Scaling based on real-time

metrics. Further guidance is available in AWS documentation on dynamic scaling Dynamic Scaling for

EC2.

For the issue of "too many connections" on a MySQL database, using RDS Proxy offers a streamlined

solution:

RDS Proxy Setup: RDS Proxy sits between your application and the database. It pools and efficiently

manages database connections, which reduces the number of direct connections to the database.

Connection Management: By handling connection pooling, RDS Proxy can help mitigate issues

related to connection overhead and limits, such as the "too many connections" error, by allowing the

database to serve more requests from a smaller and more stable number of connections.

Minimal Code Changes: Integrating RDS Proxy requires changes only to the database connection

settings in the application's configuration files to point to the RDS Proxy endpoint instead of directly

to the database. This minimizes the amount of code change needed and leverages RDS Proxy to

handle connection scaling and management more efficiently.

This approach enhances database performance and scalability by efficiently managing connections

without the need for significant application changes or database resizing.