[SOLVED] Are AWS availability zone labels the same across time/users?

Are AWS availability zone labels the same across time/users?

I'm trying to colocate my AWS instance with a website which, according to them, is hosted on availability zone ap-southeast-1c.

I'm wondering if the 1c designation is stable over time and across users? I recall reading somewhere a long time ago that it isn't, but I can't recall the source. If the designation isn't stable across time/users, how do I ensure that I've hosted within the same availabilty zone?

I'm given the following choices when creating the instance:

subnet-3dad4b75 | Default in ap-southeast-1b
subnet-bfaf02e6 | Default in ap-southeast-1c #the obvious choice, ONLY IF the 1c label is stable
subnet-dbc533bd | Default in ap-southeast-1a

Solution

Over time they're the same, but not across AWS account. From the EC2 documentation:

To ensure that resources are distributed across the Availability Zones for a Region, we independently map Availability Zones to names for each AWS account. For example, the Availability Zone us-east-1a for your AWS account might not be the same location as us-east-1a for another AWS account.