Which AWS service or feature will meet these requirements with the LEAST amount of additional coding?

Explanations:

AWS AppSync is a managed service for building GraphQL APIs. It does not support direct integration with SAML, social media authentication, or AWS services.

Amazon Cognito identity pools support federated authentication with SAML, social media providers, and allow access to AWS resources like DynamoDB.

Amazon Cognito user pools handle user authentication but do not provide direct support for AWS resource access or social media authentication without additional coding.

AWS Lambda@Edge is a serverless compute service for running Lambda functions at CloudFront locations. It is not specifically for handling SAML or social media authentication.