Which service helps improve the availability of a website through caching?

Amazon CloudFront is a content delivery network (CDN) service designed specifically to improve the availability and performance of websites and web applications through caching. It works by distributing content to multiple locations, known as edge locations, around the world. When a user requests content, CloudFront fetches it from the nearest edge location, significantly reducing the time it takes to deliver the content and improving the availability by serving cached copies.

The caching mechanism in CloudFront means that frequently accessed content can be served directly from edge locations rather than a central server, reducing latency and load on the origin server. This not only enhances the responsiveness of a website but also ensures that content remains accessible even during traffic spikes, as cached content is readily available at multiple edge locations.

In contrast, Amazon S3 serves as a storage solution but does not inherently provide caching or delivery optimization functionalities. AWS Global Accelerator improves availability and performance for global applications but does so through optimizing routes rather than content caching. AWS Direct Connect, while providing a dedicated network connection to AWS, doesn't specifically address website availability through caching but rather focuses on network connectivity. Thus, Amazon CloudFront stands out as the best choice for enhancing website availability through caching.