System.InvalidOperationException: Timeout expired. 
The timeout period elapsed prior to obtaining a connection from the pool.  
This may have occurred because all pooled connections were in use and max pool size was reached.

    public class MvcApplication : HttpApplication
    {
        private readonly IUsers _users;

        protected MvcApplication(IUsers users)
        {
            _users = users;
        }

        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();

            ControllerBuilder.Current.SetControllerFactory(new CustomControllerFactory());
        }

        protected void Application_AuthenticateRequest()
        {
            var test = _users.Test();
            //...
        }
    }