I have seen that file ids in Dropbox is prefixed with some strings like "id:" or "ns:" or "dbid:". I am new to DB and just want to know the purpose of this? And best practices to handle these ids.
These prefixes are used to identify and validate these strings across the API. E.g., the "id:" prefix is always used for a file ID, a "ns:" prefix is always used for a namespace ID, etc.
You app can store and re-use these values, but shouldn't attempt to modify them. You can see what kinds of values different parameters accept in the API documentation. E.g., you can see that the "path" parameter for the /2/files/download endpoint accepts relative paths that match '/(.|[\r\n])*', file IDs that match 'id:.*', revision values that match 'rev:[0-9a-f]{9,}', or namespace-relative paths that match 'ns:[0-9]+(/.*)?)'.