Hosting a dynamic website on AWS Amplify integrated with AWS AppSync and AWS DynamoDB

I’m trying to host a dynamic Website (Using React) on AWS Amplify.

Also, I want the website to Interact with AWS DynamoDB with GraphQL APIs.

Now for GraphQL APIs, I have used AWS AppSync.

Right now the website has been hosted successfully on AWS Training in Pune. Amplify integrated with AWS AppSync and AWS DynamoDB, using the boilerplate code generated through the commands.

Now the problem which I’m facing is

1). If I want to add custom GraphQL Resolvers to the Application, where should I write the code for the backend?