7.3Protocol Buffers

gRPC services are defined in .proto files:

syntax = "proto3";

package user;

service UserService {
    rpc GetUser(GetUserRequest) returns (UserResponse);
    rpc ListUsers(ListUsersRequest) returns (ListUsersResponse);
    rpc CreateUser(CreateUserRequest) returns (UserResponse);
    rpc UpdateUser(UpdateUserRequest) returns (UserResponse);
    rpc DeleteUser(DeleteUserRequest) returns (Empty);
}

message GetUserRequest {
    string id = 1;
}

message UserResponse {
    string id = 1;
    string name = 2;
    string email = 3;
    string role = 4;
    string created_at = 5;
}

message ListUsersRequest {
    int32 page = 1;
    int32 per_page = 2;
}

message ListUsersResponse {
    repeated UserResponse users = 1;
    int32 total = 2;
}

The .proto file is the contract. Both client and server generate code from it, ensuring type safety.