The humble layered monolith, an architecture that has stood the test of time, remains relevant and popular to this day. Variations of this style are known by different names. The “Clean Architecture” describes a variant of this style that follows the structured, modular, testable, and maintainable approach to system design this style prescribes. The “Onion Architecture” is another variation, with its choice of name a reflection of the system’s composition of layers, with each layer depending only on the layers beneath it. Even the “Hexagonal Architecture” (alternatively named “Ports and Adapters”) can describe a variation of this style.