I am interested in the offline and sync capabilities of Amazon's app-sync but I was wondering if it could be used without dynamoDB as the backend. The graphQL resolvers written in VTL for dynamoDB look atrocious. It seems it would be much nicer to use a mongo backend. Is that possible?
Yes, you can use AppSync without DynamoDB. You can use ElasticSearch out of the box (you will need to provision the ES cluster and then setup the resolvers) or you can use Lambda and pipe your data to any source, such as mySQL. Here's info on ElasticSearch: https://docs.aws.amazon.com/appsync/latest/devguide/tutorial-elasticsearch-resolvers.html