What is Cache Warming?
Warming up cache is when websites artificially fill the cache to ensure that real visitors always have access to it when needed. Essentially, it warms up the cache for visits rather than serving the first visitor a cache miss (thus the word ‘warming’, as in warming up a car engine). We’re frequently asked at Payoda if users should employ cache warming to enhance the possibility that their visitors will be provided content from the cache and, as a result, reduce page load times.
In this blog, we discuss how cache warming works and how it improves the performance of websites, webshop, or API performance.
Before we explain cache warming, it’s important to understand why it’s crucial. The primary benefit of cache warming is that it allows web pages to load faster. Efficient web page loading results in a better user experience and an enhanced website visitor experience. According to multiple studies, users have a higher propensity to view more pages on a website when pages load faster.
What is the Purpose of a Cache?
Cache is a structure that stores values for faster lookup (inodes, memory pages, disc blocks, and so on).
Cache functions by storing some brief reference in a fast search data structure (hash table, B+ Tree) or quicker access medium (RAM vs. HDD, SSD vs. HDD). To do this quick search, your cache must be able to store values.
Let’s look at what caching is and how it can help your website load faster now that we know why it’s essential. You use your web browser to request and construct a web page from the website’s server every time you visit it. The HTML element to build the page, images, content, styling, and other files are stored on the server. To generate a complete webpage, your browser sends up to 100 requests back and forth from the website’s server.
If you don’t use any caching, you’ll have to perform those requests repeatedly every time you visit that page. And everyone else who comes to that website is making the exact requests. When a large number of people access a website at the same time, the server slows down and becomes less responsive. Caching provides a solution by storing a copy of the completed web page in many locations.
Whether hosted on a single local server or through a Content Delivery Network (CDN), a cache keeps a copy of the files that comprise a web page so that visitors may be served pages more rapidly.
By caching copies of image files, CSS, and HTML pages, the origin server is not required to produce these files each time a new visitor arrives at the website. This increases page load speed while also reducing the burden on the origin server, allowing a website to serve more users at once.
What is a Cache Hit vs. a Cache Miss?
Modern websites are continuously being updated — whether it’s a media site changing the articles on their homepage or an eCommerce site updating the inventory of a particular product — files are set to expire after a specific duration, which may be a minute or an hour. Therefore, when a cached file expires, it must be re-collected from the origin server.
A “cache miss” occurs when a visitor visits a website for the first time after a cache has been put up or after a cache has expired. The cache will get the file from the origin server, deliver it to the visitor, and store it in the cache, making it a complete or warm cache. Each successive user that visits before the cache expires will be served from cache, resulting in a “cache hit” for all cached files.
To conclude, a cold cache has no files and is unprepared to serve visitors, whereas a warm cache contains files and is ready to serve visitors.
Advantages and Disadvantages of Cache Warming
It is in a company’s best interests for website visitors to encounter a cache hit and receive a rapid response. Unfortunately, after the data expires or the cache is cleaned, some users will face a cache miss unless sites use cache warming. This diminishes the visitor’s experience.
Warming up the cache includes artificially populating it to ensure that actual visitors have access to it at all times. Essentially, it warms up the cache for visits rather than serving the first visitor a cache miss. As a result, all visitors will have the same experience.
While cache warming has advantages, there are a few things to consider. Here are some of the issues that might emerge while implementing cache warming.
1. Warming Too Many Cache Servers
The system will have to set up all of these caches if the pages are cached on a CDN with several hundred edge servers. An indexing bot, often known as a crawler, can be used on the site. To ensure that each cache is filled, this crawler will have to visit the website numerous times and from multiple places. This becomes more problematic as the number of caching servers increases. It may unnecessarily raise website demand since caches must be refreshed regularly in expectation of visitors arriving, even if no real visitors arrive before the cache expires.
2. Very Short Page Lifespans
Setting up a crawler will be ineffective if the cache duration is limited to a few minutes. This is because it won’t go through the entire catalog before the pages it visits expire. In this case, a compromise must be reached: pre-loading critical site pages.
3. Not Being Able To Handle Regular Crawling
When using undersized origin servers, a crawler’s visit might result in a significant load. In essence, the crawler rarely requests pages from the origin server, putting pressure on the database of the origin server. In this instance, the best options are to minimize the number of pages browsed, slow down the crawling, or crawl at night or during lower demand times.
Furthermore, websites should try to enhance their speed through known best practices. With quick connection times and front-end optimizations in place, users will have an enhanced on-site experience even if they hit a cold cache.
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