Identifying performance bottlenecks:

Profiling tools: Modify the website through browser developer tools and react profiler with a focus on the components that seem to be causing rerender too many times. Have a glance at the features that have got the largest number of updates or rendering times.

Monitoring performance metrics: Make sure that you track the main performance metrics in order to detect a possible regression of any kind and to discover the components which display lagging performance.

Memoization and PureComponent:

Memoization: Use memoization techniques (e.g., memoization functions like useMemo or React.memo) to prevent unnecessary re-renders of components and expensive computations.

Memoization allows you to cache the results of expensive function calls and reuse them if the inputs haven't changed.

                                      
                                      import React, { useMemo } from 'react';

function MyComponent({ data }) {
  const processedData = useMemo(() => expensiveFunction(data), [data]);

  return <div>{processedData}</div>;
}
                                      
                                    

PureComponent: Consider using PureComponent or React.memo to compare prop automatically and to avoid re-rendering of functional components when unneeded. This optimization will prove the most useful for the independent parts that do not bung props in them.

                                      
                                      import React, { PureComponent } from 'react';

class MyComponent extends PureComponent {
  render() {
    return <div>{this.props.data}</div>;
  }
}

                                      
                                    

Code-splitting and lazy loading:

Code-splitting: Break your application bundle into smaller chunks using code-splitting techniques.

This allows you to load only the necessary code for the current route or component, reducing the initial bundle size and improving loading times.

                                      
                                      import { lazy, Suspense } from 'react';

const LazyComponent = lazy(() => import('./LazyComponent'));

function MyComponent() {
  return (
    <Suspense fallback={
Loading...</div>}>
       <LazyComponent />
    </Suspense>
  );
}

                                      
                                    

Lazy loading: Lazily entail components, i.e., when they are needed, and do not tight up when not required.

This will not only help you to improve the startup time of your application, but also for applications with lots of components, this will be a very great step-starter.