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.

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.

6 — Object Diagrams

How object diagrams snapshot a specific set of instances and their links at a point in time, useful for validating a class diagram against a concrete scenario.