Code refactoring
Refactoring helps improve the structural quality of the source code. It doesn't modify the functionality of the code; it just improves the structural aspect of the code quality. Refactoring makes the code cleaner, but at times it may help you improve the overall code performance. However, you need to understand that performance tuning is different from code refactoring.
The following diagram demonstrates the development process overview:

How is code refactoring done safely? The answer to this question is as follows:
- Embrace DevOps
- Adapt to test-driven development
- Adapt to behavior-driven development
- Use acceptance test-driven development