Autofac SingleInstance WebApi Performance

Question

We've improved the performance of our API's adding services without state to .SingleInstance() , but I've a question, regarding the demo code attached,

• The IBusAppService that we are using on the controller is set to SingleInstance(), but inside the BusAppService, we are using more Interfaces, for example ( IBusRepository or IBusDomainService )
• So the question is, in order to increase the performnace, should we set all interfaces to SingleInstance() inside the IBusAppService or the performance is the same because they are inside a SingleInstance??

I'll attach here some code with the workflow :

The ApiController:

    public class BusApiController : ApiController
    {
        private readonly IBusAppService _iBusAppService;
        private readonly IBusMapper _iBusMapper;
        public BusApiController(IBusAppService iBusAppService,
                                IBusMapper iBusMapper)
        {
            _iBusAppService = iBusAppService;
            _iBusMapper = iBusMapper;
        }

        [HttpGet]
        public BusResponse Get(long id)
        {
            var bus = _iBusAppService.Get(id);

            var busResponse = _iBusMapper.Convert(bus);
            return busResponse;
        }
    }


    public class BusResponse {
       public long Id { get; set; }
    }

    public interface IBusMapper
    {
        BusResponse Convert(Bus bus);
    }

    public class BusMapper : IBusMapper
    {
        public BusResponse Convert(Bus bus)
        {
            if (bus == null) return null;

            var result = new BusResponse{Id = bus.Id};
            return result;
        }
    }

    builder.RegisterType<BusAppService>().As<IBusAppService>().SingleInstance();
    builder.RegisterType<BusMapper>().As<IBusMapper>().SingleInstance(); 

The ApplicationService

public interface IBusAppService
{
    Bus Get(long id);
}

public class BusAppService : IBusAppService
{
    private readonly IBusRepository _iBusRepository;
    private readonly IBusDomainService _iBusDomainService;
    public BusAppService(IBusRepository iBusRepository, IBusDomainService iBusDomainService )
    {
        _iBusRepository = iBusRepository;
        _iBusDomainService = iBusDomainService;
    }
    public Bus Get(long id)
    {
        var bus = this._iBusRepository.Get(id);
        var busTax = this._iBusDomainService.CalculateTax(bus);

        var result = bus;
        return result;
    }
}

Answer 1

Anything consumed by a single instance service will end up being single instance due to captive dependencies . You could change them to be single instance, too, but it won't necessarily change the performance related to instantiation cost that you see now.