Low Level Design (LLD)

Low Level Design (LLD) is about deciding how the parts of a program should work together. This playlist teaches you how to turn requirements into classes, interfaces, and working code, building the design skills and reasoning needed for low level design interviews.

The syllabus spans 13 modules, moving from software design principles and UML to design patterns, concurrency, and practical system implementations. Worked design and coding lessons for 12 systems help you follow a solution from its initial structure to the details of its implementation.

What You Will Learn

Start with the SOLID principles and UML class diagrams to understand how to organize and communicate a design. Explore creational, structural, and behavioural design patterns, including Factory Method, Builder, Adapter, Decorator, Observer, Strategy, and State, and understand the problems they help solve.

You will also cover multithreading, thread pools, synchronization, locks, and deadlock prevention. Supporting topics include dependency injection, exception handling, resilience, APIs, database design and integration, and streaming protocols.

Think Through the Design

A design begins with decisions about responsibilities. In a parking lot system, for example, you need to decide how to represent vehicles and parking spaces, which component assigns a space, and how the system handles changing availability.

As you work through different systems, learn to explain why a responsibility belongs in a particular class, how components should communicate, and where a design pattern helps. Consider what happens when requirements change, an operation fails, or multiple requests access the same data.

Learn Through Design and Implementation

Work through systems such as a parking lot, logging framework, traffic signal system, vending machine, task manager, and publish-subscribe system. Continue with an ATM, hotel management system, elevator, digital wallet, ride-booking app, and music-streaming platform.

• Identify the requirements, entities, and operations for each system.
• Define class responsibilities, relationships, and interfaces.
• Follow each design through its corresponding coding implementation.
• Reason about state changes, error handling, and concurrency where relevant.
• Learn how to present your approach and explain your design trade-offs.

Who Is This Playlist For?

This playlist is suitable for developers preparing for software engineering interviews, students moving beyond OOP fundamentals, and engineers improving their software design skills. You should be comfortable coding in one programming language and understand classes, objects, interfaces, inheritance, and polymorphism. Familiarity with basic data structures will also help with implementation.

Prepare for Low Level Design Interviews

By the end, you should be able to approach LLD interview questions by clarifying requirements, identifying entities, defining class responsibilities, and implementing the core behaviour. Learn to explain your choice of design patterns, discuss trade-offs, and adapt your solution when an interviewer introduces new requirements. These skills support low level design interview preparation and help you communicate your approach during software engineering interviews.