How to send a notification to a specific device using Amplify notification

Question

I sat up notification following this doc https://docs.amplify.aws/lib/push-notifications/getting-started/q/platform/js. I can register a token on Amazon pinpoint service. My application is a chat app, so every time someone sends a message to someone, I want to send a notification to a specific device who receives the message. My question is How I can do this ? My user message data are stored in DynamoDB. So trigger Lambda function after put operation would be a good idea but I am not sure this is the solution.