For a similar relay/proxy setup for development, I've found that a metadata endpoint emulation like provided in aws-vault can make it easier to have any AWS SDK

For a similar relay/proxy setup for development, I've found that a metadata endpoint emulation like provided in aws-vault can make it easier to have any AWS SDK calls behave the same way as they would in AWS itself. You do have to assume the role that the lambda itself would normally assume and you have to allow more than just service linked execution, but you do get to test the whole IAM chain that way as well.