Best way to transfer files to Appian from a External system

We wanted to send documents to Appian from a External system with metadata of the document.

Which is the best practice

  1. Using SFTP?(Putting a DOC and its Metadata file  at SFTP location)
  2. Using S3 bucket (AWS)(Uploading the file from the external system and sending uploaded fileid+metadata as API input to Appian to download the same)

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