What interaction composition pattern is used when a central API orchestrates interactions with microservices for order processing?

The correct answer is orchestration. In the context of microservices and API interactions, orchestration refers to a centralized approach where a main service, or API, governs and coordinates the interactions between various microservices. In the case of order processing, the central API takes on the responsibility of invoking the necessary microservices, managing their interactions, and orchestrating the overall workflow to complete the order processing task.

This approach allows for streamlined communication and efficient management of the order process, as the central API can handle various components of the workflow, such as payment processing, inventory checks, and shipment tracking, in an organized manner. By orchestrating these services, the API can ensure that they work together effectively to achieve the desired outcome.

Choreography, in contrast, would involve each microservice independently knowing how to interact with others without a central authority, leading to a more decentralized model. Aggregation focuses on collecting data from different sources and presenting them as a single response, while multicasting refers to sending messages or requests to multiple recipients simultaneously. None of these options describes the controlled and organized coordination characteristic of orchestration in order processing scenarios.