Securing GraphQL APIs with AWS AppSync Lambda Authorizers in .NET

This article demonstrates how to implement AWS Lambda authorizers with Direct Lambda Resolvers in .NET for securing GraphQL APIs on AWS AppSync.

• AWS AppSync supports multiple authorization modes: API Keys, Lambda, Cognito, OIDC, and IAM
• Lambda authorizers enable custom token validation and authorization workflows in .NET
• Authorization context flows directly from AppSync to Lambda resolver functions
• Implement role-based access control (RBAC) using authorization context in resolvers
• CDK context variables enable conditional deployment with API Key or Lambda authorization
• Sample authorizer accepts "valid-token" and "admin-token" for testing different access levels
• Authorization logic can be unit tested using standard .NET testing frameworks

The post provides a complete implementation guide for securing GraphQL APIs by combining Lambda authorizers with Direct Lambda Resolvers, enabling fine-grained access control in strongly-typed .NET code.