All 15 gRPC Services questions
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What is gRPC, and how does it differ from a traditional REST/JSON API? What is the purpose of the ServerCallContext parameter present in every gRPC server method, and what information does it expose? How do you define a gRPC service contract using Protocol Buffers (.proto files), and how does code generation work in a .NET project? How do you implement a gRPC server method in ASP.NET Core, and how does it integrate with the standard hosting model? How do you implement server-streaming gRPC using C#'s IAsyncEnumerable<T> or IServerStreamWriter<T>? What is protobuf field numbering, and why must you never reuse or renumber a field once a message definition has shipped to production? How would you version a gRPC service's contract while maintaining backward compatibility with existing clients? How does client-side load balancing work for gRPC when calling a service with multiple backend instances, without a dedicated load balancer? What are the four types of gRPC service methods (unary, server streaming, client streaming, bidirectional streaming), and when is each appropriate? How does gRPC handle errors and status codes, and how does this differ from HTTP status codes in REST?
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What is gRPC-Web, and why is it needed for calling gRPC services directly from a browser-based JavaScript client?

Intermediate

Answer

Browsers don't provide the low-level HTTP/2 trailer access and full control needed for native gRPC's wire protocol, so gRPC-Web is a protocol variant designed to work within browser constraints (using standard HTTP requests the browser's fetch/XHR APIs can handle), requiring either a proxy (like Envoy) to translate between gRPC-Web and native gRPC, or ASP.NET Core's built-in Grpc.AspNetCore.Web middleware to natively accept gRPC-Web requests without a separate proxy.
builder.Services.AddGrpc();
var app = builder.Build();

app.UseGrpcWeb();  // enables gRPC-Web support directly, no separate proxy needed
app.MapGrpcService<GreeterService>().EnableGrpcWeb();
Real-world example A Blazor WebAssembly frontend calls a gRPC backend service directly using gRPC-Web support built into ASP.NET Core, avoiding the need to deploy and maintain a separate Envoy proxy just to bridge the browser-to-gRPC gap.

Common follow-ups: What specific browser limitations prevent native gRPC from working directly?;How does gRPC-Web's performance compare to native gRPC given the translation overhead?

ASP.NET Core Middleware & Request Pipeline;Blazor (Server & WebAssembly)
All 15 gRPC Services questions