Which kinds of decisions are premature? Decisions that have nothing to do with the business requirements—the use cases—of the system. These include decisions about frameworks, databases, web servers, utility libraries, dependency injection, and the like. A good system architecture is one in which decisions like these are rendered ancillary and deferrable. A good system architecture does not depend on those decisions. A good system architecture allows those decisions to be made at the latest possible moment, without significant impact.