If you are using the AWS CLI tool for your operations and design implementation/application, note that the CLI will look for Credentials & Config data in the following hierarchical order.
1. Command Line Options
For example: using options such as "--profile", "--region", "--output", and so on
2. Environmental Variables
AWS_ACCESS_KEY_ID
AWS_SECRET_ACCESS_KEY
AWS_SESSION_TOKEN
AWS_DEFAULT_REGION and so on
3. CLI Credentials File
For Linux: ~/.aws/credentials
For Windows: C:\Users\\.aws\credentials
4. CLI Configuration File
For Linux: ~/.aws/config
For Windows: C:\Users\\.aws\config