I've seen examples of DynamoDB as the data source for AWS AppSync but I'm wondering if Aurora (specifically PostgreSQL) can be used? If yes, what would the resolvers look like for a basic example? Are there any resources that demonstrate doing this for Aurora PostgreSQL or even MySQL?
You can use the AWS Lambda resolver available in AWS AppSync to access Aurora Postgres. The code is similar to how you would access a relational database using any language. For example, you could use node-postgres with NodeJS to implement the Lambda function.