I've been dealing with cross-projects service accounts recently, but I'm unable to figure out how billing works exactly, as I have no visibility on it due to org policies.
Let's say I have a project A, where I create service account X. I then add this service account to project B, where my data is stored in BigQuery, with proper roles.
If service account X is used to read 100GB of data everyday from BigQuery in project B, who gets billed for the operation? Project A or B, and/or how would you suggest to test this? I hoped to find the answer in the job response object, but it doesn't seem to be there.
It would make sense to be project A, as that service account X is a "guest" in project B with read access to the data it needs, but I don't know how to test it.
Thank you!