What Happens To Incomplete Upload Session Start Commands

All Dropbox API upload sessions expire after 48 hours. If you start one and never complete it, it will become invalid 48 hours after it was started and the data will not be committed.

If you call to finish an upload session but don't receive the response, e.g., due to a network issue, it's possible the request did still make it to Dropbox and was serviced by Dropbox, in which case the file may have been committed. You can call the API again (e.g., /2/files/get_metadata or /2/files/list_folder[/continue], for instance), to check if the file was in fact committed.

The Dropbox API does allow you to have multiple active upload sessions at the same time, so you can have multiple different upload sessions for different files and use them in parallel. Please refer to the Data Ingress Guide for information on avoiding lock contention though.

Finally, I'm not sure I understand the scenario with offset:0 that you described. If something's not working as expected, please share the relevant code and unexpected output so we can look into it. (Be sure to redact your access token though.) Thanks!