You are tasked with designing and implementing a scalable GraphQL API using Apollo Server. The API should support [QUERY_TYPE] for fetching data, [MUTATION_TYPE] for modifying data, and [SUBSCRIPTION_TYPE] for real-time updates. Ensure the schema is well-documented with clear type definitions, and implement proper error handling and authentication using [AUTH_METHOD]. Optimize performance with data loaders for [DATA_SOURCE] to avoid N+1 queries. Include unit tests with [TESTING_LIBRARY] and provide a deployment strategy for [CLOUD_PLATFORM]. The solution should follow best practices for modularity, security, and maintainability.