Which AWS service allows applications to be created entirely through code for complex system deployment?

The correct answer is AWS CloudFormation. This service enables users to create and manage AWS resources using code, allowing for the automation and effective deployment of complex applications and systems. By defining infrastructure as code, developers can describe the desired state of their architecture in templates, which are written in JSON or YAML. This approach simplifies the deployment process, promotes consistency, and allows for version control, making it easier to deploy the same environment repeatedly and manage changes over time.

AWS CloudFormation also integrates smoothly with other AWS services, enabling the orchestration of complex multi-tier applications. This capability is especially valuable for organizations striving to maintain consistency and scalability across multiple environments.

In comparison, while AWS SDKs provide tools and libraries for developers to interact with AWS services programmatically, they do not directly manage or deploy the infrastructure itself. The AWS Console is a graphical interface for managing AWS resources manually, which lacks the automation and code-driven approach of CloudFormation. AWS CloudTrail is used for monitoring AWS account activity and API usage but does not deal with resource deployment directly.