When user have been authenticated in a mobile or web application with a web identity provider (Amazon Cognito, Login with Amazon, Facebook, Google, or any OpenID Connect-compatible identity provider). AsyncAws is able to fetch Credentials from a Role assumed by the WebIdentity.
That authentication mechanism allows use of fined-grained Roles in an EKS cluster (AWS managed service for K8S). It let you assign a specific role per POD. Similar to EC2 Instance Metadata you have nothing to configure on the application, you only configure the role and permission assumed by the POD's ServiceAccount. See AWS documentation for more information.