Amazon Elastic Container Service (Amazon ECS) and AWS Fargate now allow you to use customer managed keys in AWS Key Management Service (KMS) to encrypt data stored in Fargate task ephemeral storage. Ephemeral storage for tasks running on Fargate platform version 1.4.0 or higher is encrypted with AWS owned keys by default. This feature allows you to add a self-managed security layer which can help you meet compliance requirements.
Customers who run applications that deal with sensitive data often need to encrypt data using self-managed keys to meet security or regulatory requirements and also provide encryption visibility to auditors. To meet these requirements you can now configure a customer-managed KMS key for your ECS cluster to encrypt the ephemeral storage for all Fargate tasks in the cluster. You can manage this key and audit access like any other KMS key. Customers can use this feature to configure encryption for new and existing ECS applications without changes from developers.
Source:: Amazon AWS