I've only ever worked with OCI. Is there an equivalent to their Availability Domain concept in GCP?
I have been looking through the UI and the responses from the GCP Golang Client Libraries but have found nothing relevant besides the zone which the instance is deployed in. I've read GCP's key terminology page and other documentation and am now just wondering if a concept like this even exists in GCP.
An OCI region is the same as a Google Cloud region. An OCI availability domain is the same as a Google Cloud zone. There are some differences in how networking is handled, but for most purposes, the mapping is very close.
All of the cloud vendors use similar constructs - a region consists of multiple data centers separated geographically to isolate local failures: earthquakes, power, severe weather, fires, etc.
Note: in some regions for some vendors, there is only one data center per region. As their business grows in those areas, the vendors usually have plans to add more data centers. For those areas a data center == zone/availability-domain == region.