AWS AppSync
AWS AppSync is a managed GraphQL service that simplifies application development by providing a flexible API layer for securely accessing, manipulating, and combining data from multiple sources.
Key Features
- Managed GraphQL: No GraphQL server infrastructure to maintain
- Real-time subscriptions: WebSocket-based live updates out of the box
- Offline support: Built-in conflict resolution for offline-first applications
- Multiple data sources: Connect to DynamoDB, Lambda, RDS, HTTP endpoints, and more
How It Works
- Define your GraphQL schema
- Configure data sources (databases, APIs, Lambda functions)
- Write resolvers to map GraphQL operations to data sources
- AppSync handles the rest: authentication, caching, real-time updates
Resolver Types
| Type | Description |
|---|---|
| VTL Resolvers | Velocity Template Language for direct data source access |
| JavaScript Resolvers | Modern JS runtime for complex logic |
| Pipeline Resolvers | Chain multiple resolvers for complex operations |
What We Like
- Real-time made easy: Subscriptions work without additional infrastructure
- Fine-grained security: Field-level authorization with Cognito or IAM
- Caching: Server-side caching reduces data source load
- Amplify integration: Seamless with Amplify frontend libraries
What We Don't Like
- VTL learning curve: Velocity Template Language is awkward (though JS resolvers help)
- Debugging complexity: Tracing issues through resolvers can be challenging
- Cost at scale: Per-request pricing adds up with high-volume applications
- Schema limitations: Some advanced GraphQL patterns aren't fully supported
When to Use AppSync
AppSync excels for mobile and web applications that need real-time updates, offline support, or complex data aggregation. For simpler REST APIs, API Gateway with Lambda may be more straightforward.