Hey! I strongly suggest using CAI rather than the GCP apis, it simplify a lot the collection of data and you won’t hit a road block with quotas and hidden quotas.
Pulling data from the APIs won’t scale and it’s the exact reason why we migrated off Forseti (forsetisecurity.org) , which we helped build in the first place.
Feel free to ping me if you want more details, my contact is in my profile.
It might be time to revisit that decision now though: it would be neat to have your CAI ingestion logic in Cartography :-)