public class MyClass
{
   private static MyConfig _config;
   private UnitOfWork _uow;

   static MyClass(){
        // This takes some time since it's a web service call!!!
        _config = ConfigService.GetConfig();
   }

   public MyClass(){
        _uow = CreateUow(_config.UOWConnectionString);
   }

   public Response DoSomething(){
       // logic with _uow
   }
}