Amr Samir | Pragmatic SOLID Principles vs Overengineering

1. The Overengineering Trap

When developers first learn the SOLID principles, they often fall into the trap of dogmatic over-abstraction:

Creating 15 interfaces for a single 20-line utility function.

Abstracting database repositories before validating the business domain.

Introducing Factory-Provider-Strategy patterns where a simple switch statement suffices.

code

Pragmatic SOLID = High Cohesion + Low Coupling + Explicit Boundaries
Overengineering = Endless Indirection + Premature Abstraction + Readability Loss

2. Pragmatic Breakdown of the 5 Principles

1. Single Responsibility Principle (SRP)

Misconception: "A class must only do one single tiny thing."

Pragmatic Rule: A module should be responsible to one, and only one, actor or business domain reason to change.

2. Open/Closed Principle (OCP)

Misconception: "Never touch existing code; always subclass or add interfaces."

Pragmatic Rule: Design extension points (like plugin handlers or strategy maps) around volatile business rules while keeping stable logic direct and readable.

3. Liskov Substitution Principle (LSP)

Subtypes must be substitutable for their base types without breaking invariants or throwing unexpected runtime errors.

4. Interface Segregation Principle (ISP)

Clients should not be forced to depend upon interfaces that contain methods they do not use. Prefer small, focused interfaces.

5. Dependency Inversion Principle (DIP)

High-level policy should not depend on low-level details; both should depend on abstractions. Keep your domain logic free from direct database or vendor SDK dependencies.

3. Clean vs Overengineered Example

typescript

// Pragmatic & Clean
export interface NotificationService {
  send(userId: string, message: string): Promise<void>;
}

export class EmailNotificationService implements NotificationService {
  async send(userId: string, message: string) {
    // Direct and readable implementation
  }
}

Pragmatic SOLID Principles: Writing Clean Systems Without Overengineering

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