We will use doc_type::uuid format for the Couchbase document key. The key will not be stored in the document, just in the metadata. Is there any reason to store the uuid separately in the document field (it is randomly generated, so it serves just as an id). Seemingly, one does not need to store the doc_type field either as it can be extracted from the full key in the metadata in case of a creating a view, etc.
What is recommended as best practice?