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There will be a set of marketplace APIs that the UI will use to get categories and packages. In the first version of the market, the APIs will simply be static content served from S3. This essentially amounts to placing packages in a pre-determined directory structure, and generating index files that will be used to get metadata about the packages, such as the list of all packages, list of packages in a category, versions of a package, etc. a file that lists all packages in the repository.
There will be an internal process to push the entire market repository to S3. If a user wishes to host their own marketplace, they can do so using their own S3 instance or by sticking a server like (apache httpd for example) on top of a local directory structure.
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