The correct answer is: Use the AWS Resource Groups Tag Editor to run a global query for resources tagged with the application key.

The AWS Resource Groups Tag Editor is specifically designed to search, filter, and report on AWS resources based on their tags across multiple services and Regions. It provides a fast, centralized interface that avoids the need to manually query each Region or service. This is the most efficient way to retrieve a list of all components tagged for a specific application.

Why the other options are incorrect:

Using AWS CloudTrail to find resources with a specific tag is not practical. CloudTrail logs API activity but does not provide a direct way to list resources by tag. It also involves parsing logs and is not optimized for this use case.

Querying each service and Region with the AWS CLI is technically possible but extremely inefficient and slow. It would require writing custom scripts and manually aggregating results, which contradicts the requirement for a quick solution.

Running a query in Amazon CloudWatch Logs Insights only works if the services are logging relevant tag metadata into CloudWatch Logs, which is not guaranteed. Its not designed to inventory tagged resources.

Why this question is important: This question tests your ability to efficiently retrieve resource metadata in a multi-Region, multi-service environment. Being familiar with AWS-native tools like the Tag Editor is crucial for visibility, compliance, and cost optimization tasks.

Tip: When asked to identify or report on resources based on tags across services or Regions, always consider Resource Groups Tag Editor first. It's a centralized and purpose-built tool for this exact scenario.

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