Caching Server-Side Rendered Pages in React: Techniques and Examples

Server-side rendering (SSR) has become increasingly popular in React web development, as it can improve the initial load time and search engine optimization (SEO) of a website. However, caching server-side rendered pages is important to further enhance the website's performance and reduce the load on the server. In this article, we will explore some techniques and examples of caching server-side rendered pages in React.

What is Caching?

Caching is the process of storing data temporarily in a cache so that it can be quickly retrieved when needed, rather than being retrieved from the original source every time. Caching is commonly used in web development to improve the performance of websites, as it reduces the amount of time needed to load a page and minimizes the load on the server.

Caching SSR Pages in React

Caching server-side rendered pages in React can be accomplished in a few different ways. In this section, we will explore some techniques and examples of caching SSR pages.

Browser Caching

One of the simplest ways to cache server-side rendered pages is by using browser caching. Browser caching involves storing the page data in the user's browser cache so that the page can be quickly retrieved if the user visits the page again. This is achieved by setting the appropriate HTTP headers, such as the Cache-Control header, to indicate to the browser how long to cache the page.

Here's an example of setting the Cache-Control header to cache a page for 10 minutes:

import { NextApiResponse } from 'next';

const handler = async (_req: unknown, res: NextApiResponse) => {
  const data = await fetchData();
  res.setHeader('Cache-Control', 'max-age=600');
  res.status(200).json(data);
};

export default handler;

Memory Caching

Memory caching involves storing the server-side rendered page data in memory on the server. This allows the server to quickly retrieve the page data without having to regenerate the page on subsequent requests. Memory caching is commonly used in SSR frameworks like Next.js, which provide built-in support for memory caching.

Here's an example of using the getServerSideProps function in Next.js to implement memory caching:

import { GetServerSideProps } from 'next';

export const getServerSideProps: GetServerSideProps = async () => {
  const data = await fetchData();
  return {
    props: {
      data,
    },
    // Cache the page for 10 minutes
    revalidate: 600,
  };
};

In this example, the getServerSideProps function retrieves the data needed to render the page and returns it as a prop. The revalidate option tells Next.js to cache the page for 10 minutes and revalidate it after that time has elapsed.

CDN Caching

CDN caching involves storing the server-side rendered page data in a content delivery network (CDN). A CDN is a network of servers that are distributed around the world and used to deliver content to users based on their geographic location. CDN caching can improve the performance of websites by reducing the load on the origin server and by delivering the content to users from the closest CDN server.

Here's an example of using a CDN to cache server-side rendered pages:

import { NextApiResponse } from 'next';

const handler = async (_req: unknown, res: NextApiResponse) => {
  const data = await fetchData();
  res.setHeader('Cache-Control', 's-maxage=600, stale-while-revalidate');
  res.status(200).json(data);
};

export default handler;

In this example, the Cache-Control header is set to s-maxage=600, stale-while-revalidate, which instructs the CDN to cache the page for 10 minutes (s-maxage=600) and serve stale content while the page is being revalidated (stale-while-revalidate). This allows the page to be quickly retrieved from the CDN while still ensuring that the content is up-to-date.

Cache Invalidation

Cache invalidation is the process of removing or updating cached data when it is no longer valid or accurate. Cache invalidation is important in server-side rendering to ensure that users are seeing the latest and most accurate content. There are a few different ways to invalidate cached data, including time-based expiration, version-based expiration, and manual invalidation.

Time-Based Expiration

Time-based expiration involves setting a time limit for how long cached data is valid. This is the simplest form of cache invalidation and is commonly used in browser caching and CDN caching. In the examples above, we set a time limit of 10 minutes for caching the server-side rendered page.

Version-Based Expiration

Version-based expiration involves associating a version number with cached data and invalidating the cache when a new version is available. This is commonly used in memory caching and is implemented using a cache key that includes the version number. When a new version of the data is available, the cache key is updated and the cache is invalidated.

Here's an example of using version-based expiration with memory caching:

import { GetServerSideProps } from 'next';

const CACHE_KEY = 'my-cache-key:v1';

export const getServerSideProps: GetServerSideProps = async () => {
  const data = await fetchData();
  return {
    props: {
      data,
    },
    // Cache the page for 10 minutes
    revalidate: 600,
  };
};

// Invalidate the cache when a new version is available
const invalidateCache = () => {
  const newCacheKey = 'my-cache-key:v2';
  // Invalidate the cache by setting a new cache key
  cache.set(newCacheKey, null);
};

In this example, the CACHE_KEY constant includes the version number. When a new version of the data is available, the invalidateCache function is called to update the cache key and invalidate the cache.

Manual Invalidation

Manual invalidation involves manually removing or updating cached data when it is no longer valid or accurate. This is commonly used in memory caching and can be implemented using a cache key that is manually updated when the data changes.

Here's an example of using manual invalidation with memory caching:

import { GetServerSideProps } from 'next';

let cacheKey = 'my-cache-key';

export const getServerSideProps: GetServerSideProps = async () => {
  const data = await fetchData();
  return {
    props: {
      data,
    },
    // Cache the page for 10 minutes
    revalidate: 600,
  };
};

// Manually invalidate the cache
const invalidateCache = () => {
  cacheKey = 'my-cache-key-updated';
};

In this example, the cacheKey variable is manually updated when the data changes, which invalidates the cache.

Conclusion

Caching server-side rendered pages in React is an important technique for improving website performance and reducing the load on the server. In this article, we explored some techniques and examples of caching server-side rendered pages, including browser caching, memory caching, and CDN caching. We also discussed cache invalidation techniques, including time-based expiration, version-based expiration, and manual invalidation. By implementing these techniques, you can improve the performance and reliability of your React web applications.