Under the AWS shared responsibility model, which task is the customer responsible for?

The customer is responsible for applying updates to the guest operating system on Amazon EC2 instances. This falls under the "Security in the Cloud" part of the shared responsibility model, where AWS manages the underlying infrastructure (Security of the Cloud), and the customer is responsible for what they deploy on it, including operating systems, applications, and data. Maintaining the infrastructure for AWS Lambda, updating DynamoDB instances, and maintaining Amazon S3 infrastructure are all responsibilities of AWS. Lambda, DynamoDB, and S3 are serverless or managed services where AWS handles the underlying infrastructure, operating systems, and patching, thus falling under "Security of the Cloud.