The KISS principle, Keep It Simple, Stupid, is a design principle associated with Kelly Johnson of Lockheed Skunk Works in the 1960s and later Robert C. Martin, holding that systems work best when kept simple. It favours the simplest working solution, readability over cleverness, and no complexity beyond what the current problem requires. Simpler designs reduce the cognitive load of understanding, maintaining and extending a system, and the principle pairs with YAGNI.

KISS Principle

Details
Full Name

Keep It Simple, Stupid (also: Keep It Super Simple)

Also known as

KISS, Keep It Simple

Core Concepts:

Simplicity as a design goal

Systems work best when kept simple; complexity should be avoided whenever possible

Avoid over-engineering

Don’t add complexity, abstraction, or features beyond what the current problem requires

Readability over cleverness

Code that is easy to read and understand is preferred over sophisticated but opaque solutions

Simplest working solution first

Implement the most straightforward approach that satisfies the requirements, then refine if needed

Cognitive load reduction

Simpler designs reduce the mental effort required to understand, maintain, and extend a system

Progressive enhancement

Start simple; add complexity only when justified by concrete requirements (pairs with YAGNI)

Key Proponents

Kelly Johnson (Lockheed Skunk Works, 1960s), Robert C. Martin ("Clean Code", 2008)

When to Use:

  • When facing the choice between a simple and a complex solution

  • Reviewing code for maintainability and readability

  • Designing APIs, interfaces, or data models

  • Onboarding new team members to an unfamiliar codebase

  • Refactoring code that has grown unnecessarily complicated

  • YAGNI - Don’t implement what you don’t need yet (complementary simplicity principle)

  • DRY - Eliminate redundancy to keep codebases simple and consistent

  • SOLID Principles - Structured guidelines that reinforce clean, simple designs