Applying SOLID Design Principles to Modern Backend Systems

Writing code that works is only step one. Writing code that is easy to extend, maintain, and test requires adhering to core object-oriented software engineering principles.

The SOLID Framework

1. Single Responsibility Principle (SRP): Each class should have only one reason to change.
2. Open/Closed Principle (OCP): Software entities should be open for extension, but closed for modification.
3. Liskov Substitution Principle (LSP): Derived classes must be substitutable for their base classes without altering program correctness.
4. Interface Segregation Principle (ISP): Clients should not be forced to depend upon interfaces they do not use.
5. Dependency Inversion Principle (DIP): Depend upon abstractions, not concrete implementations.

Following these guidelines dramatically reduces tech debt and simplifies unit testing!