进行异步调用的正确方法

我有一个情况，可伸缩性是最重要的。我有一个API端点，它必须调用第三方web服务，它可能需要超过10秒才能完成。我担心的是，在等待第三方请求完成时，web请求会堆积在我们的服务器上。我需要确保对"StartJob"的请求立即返回，并且作业实际上在后台运行。最好的方法是什么?

// Client polls this endpoint to find out if job is complete
public ActionResult GetResults(int jobId)
{
    return Content(Job.GetById(jobId));
}
//Client kicks off job with this endpoint
public ActionResult StartJob()
{
    //Create a new job record
    var job = new Job();
    job.Save();
    //start the job on a background thread and let IIS return it's current thread immediately
    StartJob(); //????
    return Content(job.Id);
}
//The job consists of calling a 3rd party web service which could take 10+ seconds.
private void StartJob(long jobId)
{
   var client = new WebClient();
   var response = client.downloadString("http://some3rdparty.com/dostuff");
   var job = Job.GetById(jobId);
   job.isComplete = true;
   job.Save();
}