SOLID Principles Explained: From Class Design to Distributed Systems

The SOLID principles, introduced by software engineer Robert C. Martin, provide foundational guidelines for writing scalable and maintainable object-oriented software. The five principles cover Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, and Dependency Inversion, each targeting a specific design pitfall. Developers who misapply these principles risk building either bloated 'God objects' or overly fragmented systems that are difficult to maintain. Each principle addresses a distinct anti-pattern, such as fat interfaces, hardcoded dependencies, or broken inheritance hierarchies, and prescribes a concrete refactoring approach. The guide illustrates these concepts with Java code examples and architecture diagrams spanning class-level design through distributed system architecture.