GraphQL API Design for Complex Data Relationships

I need to design a GraphQL API for our application that deals with [specific domain: e.g., educational content, healthcare records, financial transactions]. The system has complex relationships between entities including [describe 4-5 main entities and their relationships]. Help me design a comprehensive GraphQL schema that includes: 1) Type definitions for all entities with appropriate fields and relationships, 2) Query operations that support filtering, pagination, and sorting, 3) Mutation operations for creating, updating, and deleting data, 4) Subscription operations for real-time updates, 5) Custom scalars for specialized data types, 6) Input types for complex operations, 7) Interface and union types for polymorphic relationships, and 8) Proper error handling. Also address authorization concerns by suggesting how to implement field-level permissions, rate limiting strategies, and query complexity analysis to prevent abuse. Include best practices for resolver implementation and N+1 query prevention.