Aws AppSync - websockets

https://github.com/aws-samples/appsync-refarch-realtime

https://www.i-programmer.info/programming/cloud/11994-serverless-real-time-notifications-for-web-apps-in-aws.html

https://medium.com/open-graphql/aws-appsync-serverless-graphql-real-time-reference-architecture-19b16f5e9b93