best approach to design a rest web service with binary data to be consumed from the browser

My research results:

1. Single request (data included)

   The request contains metadata. The data is a property of metadata and encoded (for example: Base64).

   Pros:

   • transactional
   • everytime valid (no missing metadata or data)

   Cons:

   • encoding makes the request very large

   Examples:

   • Twitter
   • GitHub
   • Imgur

2. Single request (multipart)

   The request contains one or more parts with metadata and data.

   Content types:

   • multipart/form-data
   • multipart/mixed
   • multipart/related

   Pros:

   • transactional
   • everytime valid (no missing metadata or data)

   Cons:

   • content type negotiation is complex
   • content type for data is not visible in WADL

   Examples:

   • Confluence (with parts for data and for metadata)
   • Jira (with one part for data, metadata only part headers for file name and mime type)
   • Bitbucket (with one part for data, no metadata)
   • Google Drive (with one part for metadata and one for part data)

3. Single request (metadata in HTTP header and URL)

   The request body contains the data and the HTTP header and the URL contains the metadata.

   Pros:

   • transactional
   • everytime valid (no missing metadata or data)

   Cons:

   • no nested metadata possible

   Examples:

   • S3 GetObject and PutObject

4. Two request

   One request for metadata and one or more requests for data.

   Pros:

   • scalability (for example: data request could go to repository server)
   • resumable (see for example Google Drive)

   Cons:

   • not transactional
   • not everytime valid (before second request, one part is missing)

   Examples:

   • Google Drive
   • YouTube