A Google App Engine Datastore developer designs, builds, and maintains applications using Google's NoSQL database service, App Engine Datastore. They handle data modeling, querying, and transactions, ensuring scalability, reliability, and efficiency. They may also integrate Datastore with other Google Cloud services and external APIs. Their role includes troubleshooting, optimizing performance, and implementing security measures. They should be proficient in programming languages supported by Google App Engine, like Python, Java, PHP, and Go. They need to understand Datastore's architecture, its limitations, and how to design applications to work seamlessly with this serverless, fully managed, highly scalable, and globally distributed database.