Welcome to an interactive and hands-on course designed to help you master Low-Level Design (LLD) from scratch and prepare for interviews.

This course covers the fundamental OOP concepts, design principles, patterns, and interview problems you need to approach LLD interviews at top technology companies.

Our goal is to help you build a strong, practical understanding of object-oriented concepts and design patterns, and then apply them to real interview problems, all in one structured place.

A significant portion of the course is available for free to support the wider developer community. If you find the course valuable and want to go deeper, you can upgrade to Premium to unlock all premium concepts, problems, exercises, diagrams, videos, AI features and unlimited code submissions.

Below, you will find additional resources for LLD interview preparation, along with the course features that make learning more practical, interactive, and engaging.

You can explore the complete course roadmap on the next page.

We have more resources to help you learn curated topics, and simulate realistic LLD interviews with AI-powered feedback.

This is our popular open source LLD GitHub repository (awesome-low-level-design) with 25k+ stars. A great place to start if you are looking for free resources.

This is a companion to the GitHub repository where you can track your progress, star for revision and take notes.

Here, you can practice Low-Level Design interview problems in a realistic environment with an AI interviewer.

Clarify requirements, identify classes and relationships, write and test your code, and receive detailed feedback.

You do not need to figure out what to learn next.

This course follows a structured roadmap that takes you from fundamental object-oriented concepts to design principles, design patterns, and complete interview problems in a logical order.

You will learn:

Object-Oriented Programming Concepts

Build a strong foundation in the concepts used throughout Low-Level Design:

SOLID Principles

Learn the five fundamental principles for designing software that is easier to understand, test, extend, and maintain:

Each principle is explained using practical examples, common design mistakes, and improved implementations.

20+ Design Patterns

Learn the most commonly used creational, structural, and behavioral design patterns:

Each pattern explains:

40+ Interview Problems

Apply everything you learn to realistic interview problems such as:

Each problem walks you through the complete design process:

Class Diagrams

Class diagrams help you understand the static structure of a system.

The diagrams evolve alongside the explanation, so you can understand why each class exists, what responsibility it owns, and how it relates to the rest of the system.

Animated Sequence Diagrams

Class diagrams show how a system is structured. Sequence diagrams show how it behaves at runtime.

Animated sequence diagrams walk through object interactions one step at a time, helping you understand which object initiates an operation, which methods are called, and how information flows through the system.

Low-Level Design cannot be learned by only reading completed solutions.

The course includes focused exercises that help you practise designing individual classes and small systems from a set of requirements.

Each interview problem include hands-on implementation exercises. Your task is to implement the missing classes and methods using the design developed in the previous sections.

These exercises help bridge the gap between understanding a design and implementing it correctly.

Concept chapters and sections include quizzes designed to test whether you truly understand the material.

Each quiz provides immediate feedback so you can identify gaps in your understanding before moving forward.

Each LLD problem includes a realistic, interactive simulation to help you understand the requirements and system behavior in greater depth.

The course also includes a growing library of video lessons covering important Low-Level Design concepts, design patterns, and interview problems.

Videos provide another way to understand difficult topics through step-by-step explanations, diagrams, code examples, and practical demonstrations.

New lessons will continue to be added as the course expands.

Whether you are learning Low-Level Design for the first time, returning after a long break, or preparing for an upcoming interview, this course gives you a structured and practical path forward.

For every topic, follow this learning process:

Do not try to memorize complete solutions or class diagrams. Instead, focus on understanding the design process like how to clarify requirements, identify core entities, assign clear responsibilities, reduce coupling, and apply design patterns only when they solve a real problem.

We have tagged each chapter and problem by interview priority and how frequently it appears in coding interviews. To make the best use of your preparation time, prioritize topics marked High or Medium.

You can use the filters on the next page to quickly find and prioritize these chapters and problems.

We’re improving the content every day. If you spot an issue or have feedback, let us know.

About the Author

Ashish Pratap Singh

Software Engineer · Educator · Creator (ex-Amazon, Adobe)

Hi, I’m Ashish, the creator of AlgoMaster.io.

I built AlgoMaster to make interview preparation more structured, practical, and enjoyable.

When I first heard about LLD interviews back in 2019, there were almost no structured resources. The few that existed mostly stayed at the surface level, focused on “template solutions,” and skipped the part that actually matters in interviews.

Most resources today still lack quality and don't cover the full picture.

This course is my attempt to fill that gap and give you everything you need to confidently clear LLD interviews.