A CDN is a network of geographically dispersed servers used to deliver static content. CDN servers cache static content like images, videos, text files, etc.
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Cost: CDNs are run by third-party providers and you are charged for data transfers in and out of the CDN.
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Expiration policy: Such as any other cache tier, it should neither be too long nor too short.
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Fallback: If there is a temporary CN outage, clients should be able to detect the problem and request resources from the origin. Otherwise CDN will be a SPOF.
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Invalidating files: You can remove a file from the CDN before it expires by performing one of the following operations:
- Using APIs provided by CDN vendors.
- Use object versioning to serve a different version of the object. To version an object, you can add a parameter to the URL, such as a version number.
