Refactor the backend codebase by following the Object oriented design pattern

[Rupeshiya]

Describe the enhancement you'd like
As of now, the codebase does not follow any design pattern, so it's pretty hard to make it maintainable and flexible

Describe approaches if you have thought of any
Refactor the backend codebase by following the Object-oriented design pattern like Singleton classes, factory classes etc

Additional context
Working on it.