KISS Principle in Software Design

The KISS principle stands for Keep It Simple, Stupid. It’s a reminder that clarity matters more than cleverness. Simple code is easier to read, maintain, test, and scale.

What It Means

Do not solve problems with more complexity than needed. Avoid overengineering. Prioritize clear logic, minimal abstractions, and straightforward flows.

A Bad Example

Let’s say you want to render a list of puppies and kittens in a React component.

import React, { useState, useEffect } from "react";

// Fetch data for a specific animal type
const fetchAnimals = async (type) => {
  const response = await fetch(`/api/${type}`);
  return response.json();
};

const AnimalCard = ({ name, type }) => {
  return (
    <div>
      <h3>
        {type === "puppy" ? "Puppy" : "Kitten"}: {name}
      </h3>
    </div>
  );
};

const AnimalList = () => {
  const [puppies, setPuppies] = useState([]);
  const [kittens, setKittens] = useState([]);

  useEffect(() => {
    // Fetch each type separately
    fetchAnimals("puppies").then(setPuppies);
    fetchAnimals("kittens").then(setKittens);
  }, []);

  return (
    <div>
      {puppies.map((p) => (
        <AnimalCard key={p.id} name={p.name} type="puppy" />
      ))}
      {kittens.map((k) => (
        <AnimalCard key={k.id} name={k.name} type="kitten" />
      ))}
    </div>
  );
};

export default AnimalList;

Why It’s Not KISS

• Two separate states for puppies and kittens
• Repeats mapping and rendering logic
• Relies on dynamic string logic inside the component (type === 'puppy' ? 'Puppy' : 'Kitten')
• Requires multiple fetch calls and state updates
• Harder to extend if more animal types are added
• The structure is harder to follow and maintain

A Better Approach

Let’s refactor this to follow the KISS principle by simplifying the logic and structure.

src/
├── components/
│   ├── Cards/
│   │   └── Animal/
│   │       └── index.jsx
│   ├── Lists/
│   │   └── Animal/
│   │       └── index.jsx
│   └── Containers/
│       └── Animal/
│           └── index.jsx

//components/Cards/Animal/index.jsx

const AnimalCard = ({ name, type }) => (
  <div>
    <h3>
      {type}: {name}
    </h3>
  </div>
);

export default AnimalCard;

//components/Lists/Animal/index.jsx
import AnimalCard from "../../Cards/Animal";

// Renders a list of animal cards
const AnimalList = ({ animals }) => (
  <div>
    {animals.map((animal) => (
      <AnimalCard key={animal.id} name={animal.name} type={animal.type} />
    ))}
  </div>
);

export default AnimalList;

//components/Containers/Animal/index.jsx

import React, { useEffect, useState } from "react";
import AnimalList from "../../Lists/Animal";

// Handles fetching and preparing the list
const AnimalListContainer = () => {
  const [animals, setAnimals] = useState([]);

  useEffect(() => {
    const fetchData = async () => {
      const [puppiesRes, kittensRes] = await Promise.all([
        fetch("/api/puppies"),
        fetch("/api/kittens"),
      ]);

      const [puppies, kittens] = await Promise.all([
        puppiesRes.json(),
        kittensRes.json(),
      ]);

      const merged = [
        ...puppies.map((p) => ({ ...p, type: "puppy" })),
        ...kittens.map((k) => ({ ...k, type: "kitten" })),
      ];

      setAnimals(merged);
    };

    fetchData();
  }, []);

  return <AnimalList animals={animals} />;
};

export default AnimalListContainer;

Why This Is a Good KISS Implementation

This structure keeps the system simple and maintainable by separating responsibilities clearly:

• AnimalCard is responsible only for rendering one animal.
• AnimalList handles rendering a list of cards.
• AnimalListContainer deals with data fetching and transformation.

Each file has a single purpose, which makes the code easy to read, test, and change. The logic flows top-down without indirection or unnecessary abstractions.

Technical benefits:

• Separation of concerns
  Rendering, data fetching, and transformation are isolated. No file mixes unrelated logic.

• Scalability
  Adding another animal type requires no change to rendering logic, only updating the API and data processing.

• Reusability
  Components like AnimalCard and AnimalList can be reused with different data or contexts.

• Testability
  Each part can be unit tested in isolation. For example, AnimalCard can be snapshot tested without mocking network calls.

• Predictable flow
  No implicit logic or nested conditionals. The structure is linear and easy to debug.

This design follows the KISS principle by avoiding unnecessary complexity while still solving the problem cleanly and extensibly.

Applying KISS isn’t about writing the shortest code, it’s about writing the clearest code. By breaking responsibilities into small, focused parts, I ended up with a system that’s easier to extend, test, and understand. The simpler the structure, the less room there is for bugs and confusion.