Explain the concept of caching and how it can be used to improve performance

TL;DR

Caching is a technique used to store copies of files or data in a temporary storage location to reduce the time it takes to access them. It improves performance by reducing the need to fetch data from the original source repeatedly. In front end development, caching can be implemented using browser cache, service workers, and HTTP headers like Cache-Control.

The concept of caching and how it can be used to improve performance

What is caching?

Caching is a technique used to store copies of files or data in a temporary storage location, known as a cache, to reduce the time it takes to access them. The primary goal of caching is to improve performance by minimizing the need to fetch data from the original source repeatedly.

Types of caching

Browser cache

The browser cache stores copies of web pages, images, and other resources locally on the user's device. When a user revisits a website, the browser can load these resources from the cache instead of fetching them from the server, resulting in faster load times.

Service workers

Service workers are scripts that run in the background and can intercept network requests. They can cache resources and serve them from the cache, even when the user is offline. This can significantly improve performance and provide a better user experience.

HTTP caching

HTTP caching involves using HTTP headers to control how and when resources are cached. Common headers include Cache-Control, Expires, and ETag.

How caching improves performance

Reduced latency

By storing frequently accessed data closer to the user, caching reduces the time it takes to retrieve that data. This results in faster load times and a smoother user experience.

Reduced server load

Caching reduces the number of requests made to the server, which can help decrease server load and improve overall performance.

Offline access

With service workers, cached resources can be served even when the user is offline, providing a seamless experience.

Implementing caching

Browser cache example

<head>
  <link rel="stylesheet" href="styles.css" />
  <script src="app.js"></script>
</head>

Service worker example

self.addEventListener('install', (event) => {
  event.waitUntil(
    caches.open('v1').then((cache) => {
      return cache.addAll(['/index.html', '/styles.css', '/app.js']);
    }),
  );
});

self.addEventListener('fetch', (event) => {
  event.respondWith(
    caches.match(event.request).then((response) => {
      return response || fetch(event.request);
    }),
  );
});

HTTP caching example

Cache-Control: max-age=3600