Merge pull request #500 from UKHomeOffice/499-kiss-principle

Added keep it simple principle

docs/principles/keep-it-simple.md

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+---
+layout: principle
+order: 1
+title: Keep it simple
+date: 2025-01-08
+tags:
+  - Ways of working
+  - Software design
+  - Maintainability
+  - Reusability
+related:
+  sections:
+    - title: Related links
+      items:
+        - text: Write maintainable, reusable and evolutionary code
+          href: /principles/write-maintainable-reusable-and-evolutionary-code/
+---
+
+Keeping your code and pipelines simple makes them easier to read, self-documenting and enables incidents to be analysed and resolved faster.
+
+---
+
+## Rationale
+
+Code should be legible by a developer at any level. Creating complex and hard to read code makes it more difficult to understand, work on and ultimately fix issues.
+
+Readability is important to help others understand what the code is meant to do. If code needs to be explained often, this may be a sign that it is too complicated and should be simplified.
+
+If a developer with project experience leaves the team, the remaining team members should still be able to understand and maintain the codebase.
+
+---
+
+## Applications and Implications
+
+- Simple code enables better asynchronous communication, enabling pull requests to be more easily read and understood.
+- To avoid premature optimisation, don't write code until it's needed, whilst considering extensibility where appropriate.
+- Follow the theme and practices already established within a project, to help the existing team understand new code more easily.
+- Keeping things simple can mean using third party libraries where someone else has already solved a problem, or made something simpler to implement.
+- Multiple lines of comments could mean the code is too complicated to understand and should be refactored.
+- Following naming conventions for variables and methods helps in self documenting your code.
+- Refactoring large functions to break out key logic can improve readability as well as enabling reuse in the future. For further details, the [Write maintainable, reusable and evolutionary code principle](/principles/write-maintainable-reusable-and-evolutionary-code/) goes into greater depth.
+
+---