What architecture pattern helps manage external system interactions?

The correct choice, the Integration Service pattern, is specifically designed to manage interactions with external systems effectively. This pattern serves as an intermediary that helps to simplify the interaction with external services, ensuring that the core application can communicate with various external systems without becoming tightly coupled to their specific interfaces or processes.

By utilizing the Integration Service pattern, developers can create a dedicated service layer that abstracts the complexity of the external interactions. This allows for better organization of code, as well as the ability to handle various connectivity protocols and data formats. Moreover, this pattern supports scalability and flexibility, enabling changes to external systems with minimal impact on the internal application logic.

In contrast, while other patterns such as the Public API, Proxy, and Facade patterns can also assist with external interactions, they are not solely focused on managing these interactions in the same comprehensive manner. The Public API pattern primarily exposes application functionalities to external clients. The Proxy pattern acts as a representative or placeholder for another object, often used for adding a level of indirection or control. The Facade pattern provides a simplified interface to a more complex subsystem but is not specifically designed to accommodate the nuances of external system interactions like the Integration Service pattern does.