In a Sitecore solution containing Sitecore XC, where should the Commerce Engine be placed?

In a Sitecore solution that incorporates Sitecore XC (Experience Commerce), placing the Commerce Engine in the Project layer is appropriate because this layer is designed to contain customizations and extensions specific to unique client requirements. The Project layer serves as the implementation layer of your solution, where you bring together various components and services tailored to the business needs and functionality of the e-commerce platform.

The Commerce Engine is a critical part of the solution that provides essential e-commerce functionalities such as product catalog management, pricing, and order processing. By placing it in the Project layer, developers can easily integrate and modify the Commerce Engine to align with specific client scenarios or additional requirements as the project evolves.

Meanwhile, other layers such as the Solution layer are meant for overarching architecture and configurations, the Feature layer is often focused on smaller, reusable functionalities, and the Foundation layer generally includes core libraries and shared services. These do not provide the same level of adaptability as the Project layer does for project-specific implementations and enhancements.