Like most development teams working on modern, Sitecore projects of reasonable complexity, at the agency where I work we've followed the Helix design principles and conventions for Sitecore development in structuring the solution. This means we have 3 groups of projects: Foundation - at the lowest level, these projects may depend on each other but don't depend on any in the higher levels. Modules in the Foundation layer are business-logic specific extensions on the technology frameworks used in the implementation - e.g. Sitecore itself - or shared functionality between feature modules that is abstracted out. Feature - these are projects in the middle layer, which may depend on Foundation projects but not on any in the higher Project level and, importantly, not on each other. Projects here should map to a business domain concept or feature. We've extended the feature level in a small way by introducing the concept of sub-features. For example, for a data import ...