servicestack - Concurrent Calls to Self-hosted ServiceStack Service

Question

My ServiceHost class is inheriting from AppHostHttpListenerLongRunningBase in order to be able to process concurrent HTTP calls. However, my service is still handling concurrent API calls in a serial way. My service is self-hosted in a win32 console Application. What did I miss here? code snipit from the initialization & configure functions is below.

 public ServicesHost() : base("MiTrendz Backend Services", 500, typeof(KeywordsManager).Assembly) { }
public override void Configure(Funq.Container container)
        {
            //Signal advanced web browsers what HTTP Methods you accept
            base.SetConfig(new EndpointHostConfig
            {
                GlobalResponseHeaders =
                {
                    { "Access-Control-Allow-Origin", "*" },
                    { "Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS" },
                },
                WsdlServiceNamespace = "http://www.......",
                DebugMode = true,
            });
            container.Register(new MyService());


            container.Register<ICacheClient>(new MemoryCacheClient());
            Plugins.Add(new ValidationFeature());
            //This method scans the assembly for validators
            container.RegisterValidators(typeof(My Validator).Assembly);

        }