AppSync is a tool built by AWS for building a GraphQL API.
"AWS AppSync is a fully managed service that makes it easy to develop GraphQL APIs by handling the heavy lifting of securely connecting to data sources like AWS DynamoDB, Lambda, and more. Adding caches to improve performance, subscriptions to support real-time updates, and client-side data stores that keep off-line clients in sync are just as easy. Once deployed, AWS AppSync automatically scales your GraphQL API execution engine up and down to meet API request volumes." - AWS AppSync Dashboard