Published on May 26, 2023

Caching: What It Is, How It Works, and How Prerender Caches

Caching Guide

Website performance is crucial for both user experience and search engine optimization (SEO). Especially since Google confirmed page speed and server response are important ranking factors.

If you’re struggling to increase your site performance, this is the solution you were looking for!

Here, we’ll explore the world of caching, how it works, and how Prerender uses caching to increase your site’s performance, speed up the indexing, and unlock higher ranking potential.

What is Caching?

Caching is the process of storing information within a temporary storage/location (cache).

It is used to facilitate access to certain data for other systems on request. This process makes communication between agents (like machines, software, etc.) faster, increasing performance.

Cache mindmap and explaination

Source: Tech Target

Here’s a simple exercise you can use to understand the process better:

Imagine you live in a small village without water pipes. Your main source of water is a river that’s 1 hour away. Instead of visiting every time you’re thirsty, your village has the routine of taking water from a river (the primary source of information) and storing it in a container available in the center of the village.

That container would be known as the cache.

Thanks to this process, people can have faster access to water when they need it. Following the same process, our machines and software can also work faster and better when we use caching properly

How Does Caching Work?

Of course, unlike water, we don’t actually move data from the primary source to the secondary location.

In caching, files are duplicated and distributed across different storage systems like your machine or other servers. Although different applications use different caching styles, the core process is the same.

Here are a couple of caching examples:

  • Browser caching – It’s a common technique used to increase page speed performance by instructing the browser to store some or most of the content from a web page on your computer. This way, pages will render faster because the data is already on your machine.
  • Content delivery network (CDN) caching – A CDN allows you to cache your website’s content in its network of servers, distributing a copy of your files across multiple servers across the globe. This way, users can access your site from the nearest server available, increasing response times.
  • Search engine caching – Some search engines, like Google, take a snapshot of your page and cache it, especially if it’s a high-performing page. If, for some reason, the page is temporarily unavailable, users can use the cache version to access the information they need.

As you can see, caching has many use cases, but most of them are looking to improve performance in one way or another. In the case of Prerender, we combine two different techniques (caching and rendering) to bring your website closer to near-perfect performance.

How Prerender Caches Your Website

If you’re new to our blog, Prerender is a technical SEO tool. We solve rendering issues, missing content, and JavaScript SEO challenges by providing a fully rendered version of your website to search engines.

To accomplish this, Prerender uses a caching system that can be divided into three steps:

  1. When a search engine bot requests a page (or you submit a sitemap), Prerender will crawl said page to download all the necessary files to render your page.
  2. It’ll render your web page (or pages) and take a snapshot of the resulting page – which is not only visually rendered like in Google’s case, but it is a fully functional version of your page.
  3. It’ll send this version to the search engine and cache the snapshot for later use.

Thanks to this process, instead of having to produce the render version every time a search bot requests the page (like in the case of server-side rendering, for example), Prerender can deliver your entire page in 0.03 seconds on average, helping your site achieve a 90+/100 PageSpeed and high Core Web Vital scores.

Understanding Prerender’s Caching Concepts

After installing and testing Prerender, the entire caching process is automated. However, there are some concepts you need to understand that’ll help you better manage and monitor your website’s caching.

What is Cache Freshness?

Cache freshness refers to how recently your page has been cached. This is an important metric for dynamic pages because you want search engines to have the most recent version of your content.

Depending on how often your content changes, you’ll want to establish a different recaching interval.

When you subscribe to Prerender, you’ll have two metrics dictating your cache freshness limits:

  • Minimum Cache Freshness – Every plan has a minimum time interval you can use to recache your pages. For example, the free plan has a minimum of 3 days, so you can’t recache your page before that; while the scale up plan has a 12 hours minimum cache freshness, so you can recache your pages two times a day if you need.
  • Maximum Cache Freshness – This refers to the top number of days your pages can be cached without recaching. For example, our Start Up plan has a 7-day maximum cache freshness, so your pages will be recached at least once a week.

What is Recaching?

Recaching is the process of updating the currently cached pages with a new, recently rendered snapshot of your content, keeping your cache freshness as up-to-date as possible.

The recaching process can be triggered for many reasons:

  • Cache expiration – Time interval policy that tells Prerender how often to recache your pages. If you set it to once a day, your page will be recached every 24 hours.
  • Recache API – You can use Prerender Recache API to ask Prerender to recache one or multiple pages.

What are a Cache Miss and a Cache Hit?

When a search bot requests a page or a sitemap is uploaded, Prerender will verify whether or not we already have a cached version of your page.

If it can’t find the snapshot, it’ll count as a cache miss and start the rendering and, eventually, caching process. On the other hand, if we do find a cached snapshot, it’ll count as a cache hit, and Prerender will serve the snapshot to the search engine – or just won’t initiate a caching process in the case of a sitemap.

How Caching and Recaching Affect Your Prerender Plan?

On every paid plan, we’ll cover cache storage, so you don’t have to worry about storage fees or running out of space. This ensures you can scale your site to millions of URLs without losing any of the benefits.

Prerender Pricing - Rendering Feature

We only charge the computational power required to render your page, a process linked to caching.

In other words, every time your page gets cached (first time) or recached (second time onwards), your page is also rendered, which will count against your plan.

This is an important distinction because pages that require more frequent caching intervals will consume a higher number of “renderings” from your plan than those recaching once a month.

The same happens when adding new pages. You’ll have to take those new renders into account to use your total rendering credits most efficiently.

Wrapping Up: Avoid Caching Irrelevant (for SEO) Pages

Prerender makes it easy to solve any SEO challenge related to JavaScript, helping you to get your website indexed faster and unlock potential higher rankings.

That also means that there’s no value in Prerendering or caching pages that you don’t want search engines to access. Rather exclude those pages from getting cached and invest those rendering credits only on publicly available pages, those you want search engines to see and show in result pages.

For a more hands-on experience, get Prerender for free and play around with the different caching options. This will help you understand the whole process before committing to a paid plan.

Leo Rodriguez

Leo Rodriguez

Leo is a technical content writer based in Italy with over 4 years of experience in technical SEO. He’s currently working at as a content marketing manager. Contact him on LinkedIn.

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