It seems as though AWS have brought a new AZ online in eu-west-2 (London) today with very little fanfare or indeed without telling their support staff. It appears as eu-west-2d. No AWS docs yet reflect this change.

Wanted to give anyone who uses this region a heads up just in case - at a client site it has caused a widespread bunch of issues as a result of Terraform failures etc. Depending on your codebase resources might be torn down and recreated unexpectedly. You can argue the case for whether this should cause you issues or not given this is the cloud etc but I just wanted to try and save someone else some hours of head scratching.

aws ec2 describe-availability-zones --region eu-west-2 --all-availability-zones --query 'AvailabilityZones[].[ZoneName,ZoneID,ZoneTYpe,State,OptInStatus,Messages]' [ [ "eu-west-2a", null, null, "available", "opt-in-not-required", [] ], [ "eu-west-2b", null, null, "available", "opt-in-not-required", [] ], [ "eu-west-2c", null, null, "available", "opt-in-not-required", [] ], [ "eu-west-2d", null, null, "available", "opt-in-not-required", [] ],