Compare REST/JSON with gRPC/Protocol Buffers. When would you choose gRPC for a Go microservice?

REST and gRPC solve the same problem — remote procedure calls — but make very different trade-offs. Understanding these trade-offs is central to microservice architecture decisions.

// user.proto
syntax = "proto3";
package user;

service UserService {
    rpc GetUser(GetUserRequest) returns (User);           // unary
    rpc StreamUsers(Empty) returns (stream User);         // server streaming
    rpc BatchCreate(stream CreateUserRequest)             // client streaming
        returns (BatchCreateResponse);
    rpc Chat(stream Message) returns (stream Message);    // bidirectional
}

message GetUserRequest { int64 id = 1; }
message User {
    int64  id    = 1;
    string name  = 2;
    string email = 3;
}

// Generate Go code:
// protoc --go_out=. --go-grpc_out=. user.proto

Why Go excels at gRPC: Go's goroutine model maps naturally to gRPC's concurrent streaming model. Each RPC handler runs in its own goroutine; the Go runtime multiplexes thousands of concurrent streams efficiently. Protobuf's generated Go code is idiomatic and integrates with Go's type system. Go's standard net/http and context packages align with gRPC's design.

Decision guide: choose gRPC for internal service-to-service calls where typed contracts, performance, and streaming matter. Use REST/JSON for public APIs consumed by browsers or third parties where human readability and broad tooling matter.

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