gRPC repeated field vs stream

Question

Hi im currently looking into grpc and im curious about the use usage of a repeated field vs a stream. For example let's say i want to implement a reservation service for movie seats. The issue im facing is, that i want to inform the service for which movie i want to reserve the seats for. I can think of 2 solutions, first: I send the id of the movie with every seat i want to reserve, or with oneof at the beginning of the stream like this:

rpc ReserveSeatsForShowing(stream SeatReservationRequest) returns(Reservation);

message SeatReservationRequest{
    oneof reservationOneOf{
        int32 showingId = 1;
        SeatReservation seatReservation = 2;
    }
}

Or using a repeated field like this

rpc ReserveSeatsForShowing(SeatReservationRequest) returns(Reservation);

message SeatReservationRequest{
    int32 showingId = 1;
    repeated SeatReservation seatReservation = 2;
}

Since i haven't really worked with grpc before im not quite sure which option to choose or if other options are available.

Looking forward for your recommendations

Answer 1

For the seat reservation, I think it would make sense to use repeated field. Just like real world scenario, the request is like "I want seat A, B, C for movie X", which is more like repeated manner than streaming. thus, the payload is very small. Also, this way should use less server resource since it is a batch process.