Low Level Design

References:

Refactoring and Design Patternsrefactoring.guru

Top Low Level Design Interview Questions: Freshers & Experienced (2025) - InterviewBitInterviewBit

25 Low-Level Design Interview Questions You Must Knowwww.finalroundai.com

GitHub - ashishps1/awesome-low-level-design: Learn Low Level Design (LLD) and prepare for interviews using free resources.GitHub

SI	Section	Topics	Done
1	Introduction to LLD	What is LLD, importance, difference from HLD, typical interview expectations
2	Software Design Principles	DRY, KISS, YAGNI, modularity, abstraction, encapsulation, cohesion, coupling
3	SOLID Principles	SRP, OCP, LSP, ISP, DIP – definitions, examples in Python/C++
4	UML & Class Diagrams	Unified Modeling Language basics, class diagrams, relationships, associations, aggregations, compositions
5	Creational Design Patterns	Singleton, Factory Method, Abstract Factory, Builder, Prototype – use cases, code samples
6	Structural Design Patterns	Adapter, Decorator, Facade, Composite, Proxy, Bridge, Flyweight – structure, intent, code samples
7	Behavioural Design Patterns	Iterator, Observer, Strategy, Command, Template Method, State, Chain of Responsibility, Visitor, Mediator, Memento – intent, structure, code samples
8	Multithreading & Concurrency	Threads, thread pools, executors, synchronization, locks, deadlocks, prevention, producer-consumer problem (Python threading, C++ std::thread, mutex, etc.)
9	Dependency Injection	Concept, benefits, implementation in Python/C++
10	Best Practices in LLD	Readability, maintainability, extensibility, testability, code reviews, documentation
11	Interview Problems	Parking lot, URL shortener, library management, e-commerce cart, chat app, file system, cache, notification system, event management, inventory, and more (practice with OOP and design patterns)