SOLID Principles

Master the five SOLID principles that make code maintainable, testable, and extensible at scale.

85 minutes

8Detailed Sections

Senior Level

SOLID is an acronym for five design principles that guide object-oriented code design. Created by Robert Martin, these principles help developers write code that is easier to maintain, test, and extend.

In system design, SOLID principles translate to service boundaries, API contracts, and modular architecture. Understanding SOLID is essential for seniors because it helps design systems that scale without becoming rigid or fragile.

This section introduces the five principles and their relevance to both LLD and HLD.

Key Takeaways

S = Single Responsibility Principle (SRP)

O = Open/Closed Principle (OCP)

L = Liskov Substitution Principle (LSP)

I = Interface Segregation Principle (ISP)

D = Dependency Inversion Principle (DIP)

SOLID applied to LLD improves code testability and modularity

SOLID applied to HLD improves service independence and scalability

Anti-SOLID code exhibits code smells: rigidity, fragility, immobility

Visual Diagram

SRP -> Single reason to change
OCP -> Open to extension, closed to modification
LSP -> Subtypes must be substitutable
ISP -> Clients depend on interfaces they use
DIP -> Depend on abstractions, not concretions

All Tutorials Practice Questions

SOLID Principles

Table of Contents

What are SOLID Principles?

Key Takeaways

Visual Diagram

Single Responsibility Principle (SRP)

Open/Closed Principle (OCP)

Liskov Substitution Principle (LSP)

Interface Segregation Principle (ISP)

Dependency Inversion Principle (DIP)

Anti-Patterns & Code Smells

SOLID in Practice: System Design Alignment