Microservice architecture (MSA) is an approach to building software systems that decomposes business domain models into smaller, consistent, bounded-contexts implemented by services
UML Use Case Diagrams show a system or application; then they show the people, organizations, or other systems that interact with it; and finally, they show a basic flow of what the system or application does
The software architecture of a program or computing system is the structure or structures of the system, which comprise software elements, the externally visible properties of those elements, and the relationships among them