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Hello, everyone. Could you please explain how a CDN manages content invalidation and cache purging?
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CDNs (Content Delivery Networks) are designed to speed up website loading times by storing copies of your website's content (images, videos, etc.) on servers located closer to your users. But what happens when you update that content? That's where content invalidation and cache purging come in.
The Need for Invalidation and Purging
Imagine you have a website with a news article. When you publish it, the CDN stores a copy. If you later correct the article, you need to ensure users see the updated version, not the old one from the CDN's cache. This is where invalidation and purging come into play.
How it Works- Cache Invalidation: This is like marking the old content as "outdated" in the CDN's cache. When a user requests that content, the CDN checks and sees it's invalid. It then fetches the latest version from your origin server (where your website is hosted) and serves that to the user. The CDN also updates its cache with the new version.
- Cache Purging: This is a more forceful approach. It completely removes the old content from the CDN's cache. The next time a user requests it, the CDN has to fetch it from the origin server.
Methods of Invalidation and Purging
CDNs offer various methods to invalidate or purge content:- URL-based Invalidation: You can specify the exact URL of the content you want to invalidate or purge. This is useful for updating individual files.
- Wildcard Invalidation: You can use wildcards (like *) to invalidate or purge multiple files at once, such as all images in a specific folder.
- Tag-based Invalidation: Some CDNs allow you to tag content with labels. You can then invalidate or purge content based on these tags, which is helpful for managing related content.
- API-based Invalidation: Most CDNs provide APIs that allow you to programmatically invalidate or purge content. This is useful for automating the process, such as when you update content in your CMS.
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