Quick Decision Tree: Which to choose? Public APIs / external clients → REST (simple, widely compatible). Internal service-to-service (microservices) → gRPC (typed, fast, low-latency). Streaming data pipelines → gRPC streaming or SignalR (depending on consumer type). Frontend-heavy apps (Blazor/React) → GraphQL if you want client-driven queries; otherwise REST with projections is simpler. Real-time dashboards, chat, trading feeds → SignalR/WebSockets . ...