How do I prepare for low level system design?

Preparing for low-level system design interviews, also known as object-oriented design or software design interviews, involves focusing on the design of classes, interfaces, functions, and other internal components of a system. It's about how to structure your code and design software components effectively. Here's a structured approach to preparing for these interviews:

1. Understand Object-Oriented Design Principles:

• Core Principles: Be familiar with object-oriented design principles like encapsulation, abstraction, inheritance, and polymorphism.
• Design Patterns: Learn about common design patterns like Singleton, Observer, Factory, Strategy, etc. Understand when and how to use them.

2. Practice Designing Classes and Interfaces:

• Take real-world scenarios or simple systems (like a library management system, a parking lot, or an online shopping system) and practice designing the class hierarchy and interfaces.
• Focus on defining classes, their attributes, methods, and the relationships between them.

3. Master UML Diagrams:

• Learn to draw Unified Modeling Language (UML) diagrams. Practice creating class diagrams and sequence diagrams, which are often used to represent system designs.

4. Work on Coding Skills:

• While low-level design isn't always about writing code, being proficient in a programming language helps you understand how your design can be implemented.
• Practice implementing design patterns in code.

5. Review SOLID Principles:

• Study SOLID principles (Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, Dependency Inversion) as they are crucial in creating maintainable, scalable, and flexible code.

6. Solve Real-World Design Problems:

• Practice with real-world problems. For example, design a chess game, an ATM machine, or a flight reservation system.
• Focus on how each component interacts with others, how data flows through the system, and how to make the system flexible and maintainable.

7. Practice Explaining Your Design:

• Clearly articulate your design choices. Be prepared to explain why you chose a particular design, how it works, and what the alternatives are.
• Practice explaining your designs to friends or mentors, or record yourself to critique your explanations.

8. Mock Interviews:

• Engage in mock interviews focusing on system design. You can use platforms like Design Gurus to practice with peers or find mentors who can provide feedback.

9. Read and Analyze Code:

• Reading well-designed code helps you understand good design practices. Open-source projects can be a good resource for this.
• Analyze what makes the codebase maintainable, scalable, and efficient.

10. Stay Updated:

• Keep up with the latest trends and best practices in software design and development.

During the Interview:

• Clarify Requirements: Make sure you understand the problem before jumping into the design.
• Think Aloud: Explain your thought process as you design.
• Be Adaptable: Be open to feedback and ready to adjust your design if the interviewer suggests changes or points out issues.

Low-level system design interviews assess your ability to design clean, efficient, and logical software components. The key to success is a solid understanding of object-oriented principles, the ability to apply design patterns appropriately, and clear communication of your design choices.

Ref: Grokking the Object Oriented Design Interview