17 Fundamental Design Principles Interview Questions and Answers (2024)
Blog / 17 Fundamental Design Principles Interview Questions and Answers (2024)
Design principles are a must have for every developer.
Not only are they a great way to go about making better code and system design choices...
They are also a great way to show off to interviewers that you know you're fundamentals.
This blog will get you up to speed so that you can nail your next tech interview.
What is SOLID?
Junior
- SOLID Principles: SOLID is an acronym that represents a set of five design principles coined by Robert C. Martin (Uncle Bob). These principles promote modular, maintainable, and extensible code:
- Single Responsibility Principle (SRP): A class should have only one reason to change.
- Open/Closed Principle (OCP): Software entities should be open for extension but closed for modification.
- Liskov Substitution Principle (LSP): Subtypes must be substitutable for their base types.
- Interface Segregation Principle (ISP): Clients should not be forced to depend on interfaces they do not use.
- Dependency Inversion Principle (DIP): High-level modules should not depend on low-level modules; both should depend on abstractions.
Explain DRY.
Junior
- DRY (Don't Repeat Yourself): This principle emphasizes avoiding code duplication by promoting code reuse. It suggests that functionality or logic should be implemented in a single, reusable place to reduce redundancy, improve maintainability, and make changes easier.
Explain KISS.
Junior
- KISS (Keep It Simple, Stupid): The KISS principle advocates simplicity in design and discourages unnecessary complexity. It suggests that software should be kept as simple as possible, avoiding over-engineering or over-complication, making it easier to understand, maintain, and debug.
Explain the Fail-Fast Principle.
Junior
- Detect and report errors as early as possible in the software development process to minimize the impact and cost of fixing them.
Explain TDD.
Junior
- Write tests before implementing features to ensure correctness and maintainability.
What is the "Tell, Don't Ask" principle in object-oriented programming?
Junior
- "Tell, Don't Ask" advises that instead of asking an object for its state and then making decisions based on that state, you should tell the object what you want it to do and let it make decisions internally. This principle promotes encapsulation and helps to hide implementation details. It leads to more object-oriented and maintainable code.
What is "Cohesion" in software design, and why is it important?
Mid
- Cohesion refers to the degree to which the elements within a module or class are related to each other. High cohesion indicates that elements work closely together to perform a specific task, while low cohesion suggests that elements are less related. High cohesion is essential because it leads to more maintainable and understandable code by grouping related functionality together.
Explain composition over inheritance.
Mid
- Composition over Inheritance: This principle promotes favoring object composition (building complex objects by combining simpler ones) over class inheritance. It helps to achieve flexibility, loose coupling, and easier maintenance by reducing the dependencies introduced through inheritance hierarchies.
Explain Separation of Concerns.
Mid
- Separation of Concerns (SoC): SoC advocates dividing a software system into distinct sections or modules, each addressing a separate concern or responsibility. This principle improves code organization, modularity, and maintainability by ensuring that each module has a clear and single purpose.
Explain the concept of "High Cohesion and Low Coupling" in software design.
Mid
- High Cohesion refers to the idea that the elements within a module or class should be closely related and work together to perform a specific task. Low Coupling, on the other hand, suggests that modules or classes should have minimal interdependence or connections with other modules. Achieving high cohesion and low coupling leads to more maintainable and modular code.
What is the "Principle of Least Astonishment" in user interface design?
Mid
- The "Principle of Least Astonishment" suggests that the behavior of a user interface should match users' expectations. It means that users should not be surprised or confused by how a system or interface works. Following this principle ensures a more intuitive and user-friendly design.
What do you understand by the Open-Closed Principle (OCP)?
Mid
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Explain the Law of Demeter.
Mid
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Explain the concept of "Defensive Programming" and its relationship with software design principles.
Senior
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Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.
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Explain the "Principle of Least Privilege" in software security and design. How does it relate to the principle of encapsulation?
Senior
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Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.
What is the "Principle of Idempotence" in software design? How does it contribute to robust and reliable systems?
Senior
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Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.
Explain Dependency Injection.
Senior
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Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.