Peculiar behaviour on buckets in ap-southeast-4 (Melbourne) region

Question

API keys used have full AdministratorAccess privileges, and the Melbourne region is enabled for the account. For historical reasons the account's "home" region, as set in `~/.aws/config` is Sydney.

```
$ aws configure get region
ap-southeast-2
$ 
```

Create some buckets all around the world, don't worry about encryption or policies or ACLs or anything like that:

```
$ aws s3api create-bucket --bucket aaaa-monday-bucket-sydney --create-bucket-configuration LocationConstraint=ap-southeast-2
{
    "Location": "http://aaaa-monday-bucket-sydney.s3.amazonaws.com/"
}
$ aws s3api create-bucket --bucket aaaa-monday-bucket-melbourne --region ap-southeast-4 --create-bucket-configuration LocationConstraint=ap-southeast-4
{
    "Location": "http://aaaa-monday-bucket-melbourne.s3.amazonaws.com/"
}
$ aws s3api create-bucket --bucket aaaa-monday-bucket-tokyo --region ap-northeast-1 --create-bucket-configuration LocationConstraint=ap-northeast-1
{
    "Location": "http://aaaa-monday-bucket-tokyo.s3.amazonaws.com/"
}
$ aws s3api create-bucket --bucket aaaa-monday-bucket-london --region eu-west-2 --create-bucket-configuration LocationConstraint=eu-west-2
{
    "Location": "http://aaaa-monday-bucket-london.s3.amazonaws.com/"
}
$ aws s3api create-bucket --bucket aaaa-monday-bucket-saopaulo --region sa-east-1 --create-bucket-configuration LocationConstraint=sa-east-1
{
    "Location": "http://aaaa-monday-bucket-saopaulo.s3.amazonaws.com/"
}
$ aws s3api create-bucket --bucket aaaa-monday-bucket-singapore --region ap-southeast-1 --create-bucket-configuration LocationConstraint=ap-southeast-1
{
    "Location": "http://aaaa-monday-bucket-singapore.s3.amazonaws.com/"
}
$ aws s3api create-bucket --bucket aaaa-monday-bucket-canada --region ca-central-1 --create-bucket-configuration LocationConstraint=ca-central-1
{
    "Location": "http://aaaa-monday-bucket-canada.s3.amazonaws.com/"
}
$ aws s3api create-bucket --bucket aaaa-monday-bucket-ohio --region us-east-2 --create-bucket-configuration LocationConstraint=us-east-2
{
    "Location": "http://aaaa-monday-bucket-ohio.s3.amazonaws.com/"
}
$ aws s3 ls
2023-04-17 10:55:15 aaaa-monday-bucket-canada
2023-04-17 10:42:13 aaaa-monday-bucket-london
2023-04-17 10:39:32 aaaa-monday-bucket-melbourne
2023-04-17 10:56:41 aaaa-monday-bucket-ohio
2023-04-17 10:42:44 aaaa-monday-bucket-saopaulo
2023-04-17 10:53:19 aaaa-monday-bucket-singapore
2023-04-17 10:39:05 aaaa-monday-bucket-sydney
2023-04-17 10:41:38 aaaa-monday-bucket-tokyo
.
.
.
$
```

Upload an object to each of the buckets:

```
$ echo test > test.txt
$ for i in canada london melbourne ohio saopaulo singapore sydney tokyo; do echo $i; echo "==="; aws s3 cp test.txt s3://aaaa-monday-bucket-$i ; echo; done
canada
===
upload: ./test.txt to s3://aaaa-monday-bucket-canada/test.txt

london
===
upload: ./test.txt to s3://aaaa-monday-bucket-london/test.txt

melbourne
===
upload failed: ./test.txt to s3://aaaa-monday-bucket-melbourne/test.txt An error occurred (IllegalLocationConstraintException) when calling the PutObject operation: The ap-southeast-4 location constraint is incompatible for the region specific endpoint this request was sent to.

ohio
===
upload: ./test.txt to s3://aaaa-monday-bucket-ohio/test.txt

saopaulo
===
upload: ./test.txt to s3://aaaa-monday-bucket-saopaulo/test.txt

singapore
===
upload: ./test.txt to s3://aaaa-monday-bucket-singapore/test.txt

sydney
===
upload: ./test.txt to s3://aaaa-monday-bucket-sydney/test.txt

tokyo
===
upload: ./test.txt to s3://aaaa-monday-bucket-tokyo/test.txt

$ 
```

Why does Melbourne fail?

It works when the region is added as a flag, but why the need to do this for Melbourne and not anywhere else?

```
$ aws s3 cp test.txt s3://aaaa-monday-bucket-melbourne --region ap-southeast-4
upload: ./test.txt to s3://aaaa-monday-bucket-melbourne/test.txt
$ 
```

Accepted Answer

I tried running it with the "--debug" option in my environment.  
For reasons unknown, they were trying to send it toward S3 in the default region.  
For example, if the default region is "ap-northeast-1", the endpoint would be something like "https://aaaa-monday-bucket-melbourne.s3.ap-northeast-1.amazonaws.com:443".  
The above may be a bug.

Answer

What does `aws s3api get-bucket-location --bucket aaaa-monday-bucket-melbourne` return?  I see under `aws s3api create-bucket help` that ap-southeast-4 isn't listed in the LocationContraint syntax.  Maybe the doco is out of date, or maybe it really doesn't work?

Peculiar behaviour on buckets in ap-southeast-4 (Melbourne) region

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