Modern GraphQL APIs are essential for modern applications that require data from multiple sources, which are often backed by different databases and fronted by various REST APIs. GraphQL provides a complete description of the data in an API, allowing clients to ask for exactly what they need while making it easier to evolve APIs over time. MongoDB Atlas is a modern developer data platform with a fully managed cloud database that complements popular development stacks like MEAN and MERN, aggregating data from multiple origins into a single source. AWS AppSync allows developers to build GraphQL and Pub/Sub APIs, enabling real-time interactions in applications and providing serverless scalability. By integrating MongoDB Atlas and AWS AppSync, developers can create scalable GraphQL APIs by consolidating multiple REST APIs and data sources on AWS, offering flexibility in defining the structure of the data while reducing payload size. The solution involves using Lambda Resolvers to translate GraphQL requests and retrieve data from MongoDB Atlas, with options to use the Atlas Data API or connect directly via MongoDB drivers.