Modernizing SignalR with AWS AppSync Event API

This article explains how to migrate from SignalR to AWS AppSync Event API for real-time .NET applications, replacing self-managed infrastructure with serverless WebSocket communication.

• AppSync Event API eliminates Redis backplane and always-on server infrastructure costs
• Automatic scaling handles millions of concurrent WebSocket connections without configuration
• Backend publishes events via HTTP POST; frontend subscribes using AWS Amplify over WebSocket
• Hierarchical channel naming organizes events by domain without additional backend logic
• Use IAM roles for production, API keys for development; rotate credentials via Secrets Manager
• Keep event payloads under 128 KB; publish references for large datasets instead
• Monitor PublishErrors, SubscriptionErrors, and ConnectionDrops metrics in CloudWatch
• Best suited for publisher-to-many-subscribers patterns, not bidirectional RPC communication

Migration reduces operational overhead and improves developer productivity by shifting infrastructure management to AWS while maintaining low-latency real-time communication.