Single Responsibility Principle
Each class should have only one reason to change. Design classes that do one thing well and are easy to maintain and test. Essential for writing clean, maintainable code in interviews.
Practice low-level design interviews with AI. Solve OOP design problems including SOLID principles, design patterns, and classic problems like Parking Lot, Elevator, Hotel Management, ATM, and more. Get real-time feedback from AI evaluation.
Low-Level Design (LLD) interviews test your ability to design software components at the implementation level. These interviews evaluate your understanding of object-oriented design, design patterns, SOLID principles, and your ability to write clean, maintainable code.
Problems are categorized by difficulty level: SDE1 (entry-level), SDE2 (mid-level), SDE3 (senior), and SENIOR+ (staff level). Practice across all difficulty levels to prepare for interviews at your target level.
Low Level Design (LLD) is the art of translating high-level requirements into concrete, maintainable code architecture. It covers Object-Oriented Programming (OOP) principles — encapsulation, inheritance, polymorphism, and abstraction — alongside SOLID principles and classic GoF design patterns like Singleton, Observer, Strategy, Factory, and Decorator.
In technical interviews at top product companies, LLD rounds test your ability to design real-world systems such as a Parking Lot, Elevator System, or Library Management System from scratch under time pressure. Practicing with an AI mock interviewer lets you get immediate, objective feedback on your class hierarchies, design choices, and code quality.
InstaMock's AI evaluates your submissions against SOLID principles, correct use of design patterns, code extensibility, and readability. Whether you are preparing for SDE1 or targeting a Senior Engineer role, our graded problem set helps you build the muscle memory needed to ace any LLD interview.
Each class should have only one reason to change. Design classes that do one thing well and are easy to maintain and test. Essential for writing clean, maintainable code in interviews.
Software should be open for extension but closed for modification. Use inheritance and composition to add new features without changing existing code. Demonstrates advanced OOP knowledge.
Derived classes must be substitutable for base classes. Implement inheritance correctly so any derived class can replace the base class in any context. Key for designing robust inheritance hierarchies.
Many client-specific interfaces are better than one general interface. Design focused, minimal interfaces that clients actually depend on. Reduces coupling and improves flexibility.
Depend on abstractions, not concrete implementations. Use dependency injection to create loosely coupled, testable systems. Advanced OOP pattern tested in senior engineer interviews.
Master Singleton, Factory, Abstract Factory, Builder, and Prototype patterns. Understand when to use each for creating objects efficiently and maintaining flexibility. Foundation of OOP design patterns.
Learn Adapter, Bridge, Composite, Decorator, Facade, Flyweight, and Proxy patterns. Solve problems where objects need to be composed or their relationships modified without changing their structure.
Master Chain of Responsibility, Command, Iterator, Mediator, Memento, Observer, State, Strategy, Template Method, and Visitor patterns. Design interactions between objects and distribute responsibility effectively.
Practice object-oriented design problems with AI-powered code evaluation.