Google Drive API: Queries per x seconds per user

Question

The Google Drive API has a quota called Queries per 100 seconds *per user* - but what exactly is a user? Is it per OAuth 2.0 client ID, or is it per source IP?

Answer 1

As what stated in the note:

Note: Per-user quotas are always enforced by the Drive API. If the quotaUser and userIp parameters are omitted, the quota user is determined by the access token in the request.