What signs indicate inefficient or incorrect system architecture?

Signs of ineffective or incorrect system architecture may include:

• Support and extension complexity: changes require significant effort and have many side effects.
• Poor modularity: components are highly coupled, making it difficult to isolate parts.
• Low performance: architecture does not consider speed and resource requirements.
• Lack of scalability: system struggles with increasing load or data volume.
• Code and logic duplication: functionality is repeated in different places.
• Poor readability and documentation: difficult to understand how the system is structured.
• Lack of testability: difficult to write and run automated tests.

For example, if in an iOS app all business logic and UI are tightly coupled in one class, it complicates support and testing, which is a sign of poor architecture.