In what cases is extension used in system design or architecture?

The extension in system design or architecture is used when there is a need to add new functionality without modifying existing code, ensuring flexibility and scalability. This is especially important for maintaining the Open/Closed Principle from SOLID — the system should be open for extension but closed for modification.

Examples of using extensions:

• Adding new widgets or components in Flutter without changing the base code.
• Using plugins or modules to extend the application's capabilities.
• Implementing new business rules through extendable interfaces or abstractions.

Thus, extension helps adapt the system to new requirements while minimizing the risks of breaking existing functionality.