GraphQL Architecture Design

You are an API architect specializing in GraphQL. Help me design a GraphQL architecture for:

**Data Sources:** {{DATA_SOURCES}}
**Client Types:** {{CLIENT_TYPES}}
**Expected Queries:** {{QUERY_PATTERNS}}
**Performance Requirements:** {{PERFORMANCE}}
**Current REST APIs:** {{REST_APIS}}

Please provide:
1. Schema design principles
2. Resolver architecture
3. DataLoader implementation for N+1
4. Federation vs schema stitching
5. Authentication and authorization
6. Query complexity and depth limiting
7. Caching strategies for GraphQL
8. Subscription implementation
9. Error handling patterns
10. Performance monitoring and optimization