[Bedrock] AWS Bedrock Client Region Identification

Hello.

How does AWS Bedrock identify the client region when accessing the API from a different region?

The region specified in the code will take priority when accessing the region.
In other words, if you specify the following, you will access "eu-west-2".

client = boto3.client('bedrock-runtime', region_name='eu-west-2')

If the region is not specified in the code, it will use the region set in the environment variable or AWS config file.
Also, in the case of EC2, the region is obtained from metadata, so if it is not specified in the code, it will access the region in which EC2 is running.
https://docs.aws.amazon.com/sdkref/latest/guide/feature-region.html

If no Region is explicitly specified for the client in the code itself, the client defaults to using the Region that is set through the following region setting. However, the active Region for a client can be explicitly set for any individual client object. Setting the Region in this way takes precedence over any global setting for that particular service client. The alternative Region is specified during instantiation of that client, specific to your SDK (check your specific SDK Guide or your SDK's code base).

In the case of ECS or Lambda, I think it is read from an environment variable called "AWS_DEFAULT_REGION".
This environment variable stores the region in which ECS or Lambda is running.
https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html#configuration-envvars-runtime
https://docs.aws.amazon.com/AmazonECS/latest/developerguide/ecs-environment-variables.html

For example, if you run the following code on an EC2 instance in each region, you can check the region you are accessing.

import boto3

bedrock = boto3.client('bedrock-runtime')

print(bedrock._client_config.region_name)

Which region's quota limits apply when accessing the Bedrock Runtime API from a different region using the specified region_name in the client?

The quota will be based on the region you are accessing.
For example, if you are accessing "eu-west-2", the quota for "eu-west-2" will be used.