Introduction

Material-UI (MUI) provides a modern styling solution for React applications, but improper usage of dynamic styles, inefficient component updates, and excessive prop drilling can lead to performance issues. Common pitfalls include re-creating styles on every render, using inline styles instead of `sx` prop, and failing to memoize expensive computations. These issues become particularly problematic in enterprise-scale applications, real-time UI updates, and complex layouts where rendering efficiency is critical. This article explores advanced troubleshooting techniques, performance optimization strategies, and best practices for Material-UI applications.

Common Causes of Slow Rendering and UI Lag in Material-UI

1. Excessive Re-Renders Due to Inline Styles

Defining styles within the component function causes re-renders on every state change.

Problematic Scenario

// Styles defined inside the component
const ButtonComponent = ({ label }) => {
    const buttonStyle = { backgroundColor: "blue", padding: "10px" };
    return <Button style={buttonStyle}>{label}</Button>;
};

The inline `style` object is re-created on each render, causing unnecessary updates.

Solution: Use the `sx` Prop for Efficient Styling

// Using MUI sx prop
const ButtonComponent = ({ label }) => {
    return <Button sx={{ backgroundColor: "blue", padding: "10px" }}>{label}</Button>;
};

The `sx` prop leverages the Emotion CSS-in-JS engine for optimized styling.

2. Performance Bottlenecks Due to Unoptimized Theme Overrides

Applying deep theme overrides leads to inefficient re-renders.

Problematic Scenario

// Deeply nested theme overrides
const theme = createTheme({
    components: {
        MuiButton: {
            styleOverrides: {
                root: {
                    backgroundColor: "blue",
                    fontSize: "16px",
                },
            },
        },
    },
});

Overriding deeply nested styles at the theme level can cause performance degradation.

Solution: Use `sx` or Component-Level Styles Instead

// Optimized component-level styles
const ButtonComponent = () => {
    return <Button sx={{ backgroundColor: "blue", fontSize: "16px" }}>Click Me</Button>;
};

Component-level styles avoid unnecessary theme re-processing.

3. Inefficient Prop Drilling Causing Unnecessary Renders

Passing props multiple levels down forces unnecessary re-renders.

Problematic Scenario

// Prop drilling through multiple components
const Parent = () => {
    const [themeColor, setThemeColor] = useState("blue");
    return <Child themeColor={themeColor} />;
};

const Child = ({ themeColor }) => {
    return <GrandChild themeColor={themeColor} />;
};

const GrandChild = ({ themeColor }) => {
    return <Button sx={{ backgroundColor: themeColor }}>Click Me</Button>;
};

Any change to `themeColor` in `Parent` forces re-renders in all child components.

Solution: Use React Context for State Management

// Using React Context API
const ThemeContext = createContext();

const Parent = () => {
    const [themeColor, setThemeColor] = useState("blue");
    return (
        <ThemeContext.Provider value={themeColor}>
            <Child />
        </ThemeContext.Provider>
    );
};

const GrandChild = () => {
    const themeColor = useContext(ThemeContext);
    return <Button sx={{ backgroundColor: themeColor }}>Click Me</Button>;
};

Using Context API prevents unnecessary renders in intermediate components.

4. High CPU Usage Due to Expensive Computations in Components

Running expensive operations inside components slows down rendering.

Problematic Scenario

// Expensive computation inside component
const ExpensiveComponent = ({ number }) => {
    const computeFactorial = (num) => {
        return num <= 1 ? 1 : num * computeFactorial(num - 1);
    };
    
    return <p>Factorial: {computeFactorial(number)}</p>;
};

The factorial function recalculates on every render.

Solution: Use `useMemo` to Cache Expensive Computations

// Using useMemo to avoid unnecessary recalculations
const ExpensiveComponent = ({ number }) => {
    const result = useMemo(() => {
        const computeFactorial = (num) => {
            return num <= 1 ? 1 : num * computeFactorial(num - 1);
        };
        return computeFactorial(number);
    }, [number]);
    
    return <p>Factorial: {result}</p>;
};

Using `useMemo` ensures calculations only run when needed.

5. Slow List Rendering Due to Lack of Virtualization

Rendering large lists without optimization causes UI lag.

Problematic Scenario

// Large list without optimization
const ItemList = ({ items }) => {
    return (
        <ul>
            {items.map((item) => (
                <li key={item.id}>{item.name}</li>
            ))}
        </ul>
    );
};

Rendering all items at once affects performance.

Solution: Use Virtualized Rendering

// Using react-window for virtualized rendering
import { FixedSizeList as List } from "react-window";

const ItemList = ({ items }) => {
    return (
        <List height={400} itemCount={items.length} itemSize={35} width={300}>
            {({ index, style }) => (
                <div style={style}>{items[index].name}</div>
            )}
        </List>
    );
};

Using `react-window` ensures only visible items are rendered.

Conclusion

Material-UI applications can suffer from performance bottlenecks, unnecessary re-renders, and high CPU usage due to inefficient state management, excessive styling calculations, and lack of memoization. By optimizing styles with `sx`, using Context API, memoizing expensive computations, implementing virtualized rendering, and leveraging `React.memo`, developers can significantly improve MUI performance. Regular profiling with React DevTools helps detect and resolve inefficiencies proactively.