Low-Level Design for MAANG Interviews

A book-shaped table of contents for LLD interview prep: OOP fundamentals through SOLID, design principles, UML, design patterns, dependency management, reliability, concurrency, domain modeling, API design, testing, refactoring, classic interview problems, advanced architecture, and performance — cross-linking Object-Oriented Programming and Patterns instead of duplicating them.

2 — Class Diagrams

How class diagrams capture a design's static structure — classes, attributes, methods, and the relationships between them — before any code gets written.

3 — Sequence Diagrams

How sequence diagrams trace the message flow between objects over time to check that a design actually satisfies a use case.

4 — State Diagrams

How state diagrams model an object's lifecycle as a finite set of states and transitions, useful for anything with a status field.

5 — Activity Diagrams

How activity diagrams map the control flow and branching logic of a workflow or business process, independent of any single class.