Partitioning monolithic architectures into decoupled, autonomous subsystems is an important concept in Object-Oriented Analysis and Design (OOAD). A monolithic architecture is a software design where all the components of an application are tightly integrated into a single codebase and deployed as one unit. While this approach is simple for small applications, it becomes difficult to manage as the system grows. Large monolithic applications often face problems such as complex code, long deployment cycles, limited scalability, and difficulty in maintaining or updating individual features. To overcome these limitations, software engineers partition the monolithic system into smaller, independent, and autonomous subsystems. The partitioning process begins by analyzing the existing application and identifying logical business domains. Domain-driven design principles are often used to define clear boundaries between different functional areas. Each subsystem is designed to perform a specific business function, such as user management, payment processing, inventory management, reporting, or customer services. These subsystems are called decoupled because they have minimal dependencies on one another and communicate through well-defined interfaces. Object-Oriented Analysis plays a significant role in identifying classes, objects, responsibilities, and relationships within the system. By studying use cases, class diagrams, sequence diagrams, and interaction diagrams, designers can determine which classes belong together and should form a cohesive subsystem. High cohesion within a subsystem and low coupling between subsystems are the primary design goals. High cohesion ensures that related functionalities remain together, while low coupling minimizes the impact of changes across different modules. Autonomous subsystems are independently developed, tested, deployed, and maintained.