AWSSDK.Transcribe StartTranscriptionJob completion

I wrote the following code that uses AWSSDK.Transcribe to transcribe audio files.
The code executes and returns the response with OK status, BUT the object response.TranscriptionJob.Transcript is null
The explanation I came up with is that it only indicated the start of the job and a colleage tells me that I need either poll now for results or use AWS Step Functions or AWS Lambda to monitor the job completion... Is there any other options for me to use in order to know when the transcription is done?

    public static string Transcribe(string inputAudioFilePath)
    {
        var awsCredentials = new BasicAWSCredentials(accessKey, secretKey);
        // North CA, for streaming "us-west-2"
        var config = new AmazonTranscribeServiceConfig { RegionEndpoint = RegionEndpoint.GetBySystemName("us-west-2") }; 

        AmazonTranscribeServiceClient client = new AmazonTranscribeServiceClient(awsCredentials, config);
        client.AfterResponseEvent += Client_AfterResponseEvent;

        var jobName = String.Format("AWSSTT-{0}", DateTime.Now.ToString("yyyy-MM-dd-hh-mm-t"));
        var inputLanguage = "en-US";

        #region Upload File to S3 Bucket

        string s3BucketName = "tts-experiment";
        string s3KeyName = inputAudioFilePath;


        mAmazonS3Client = new AmazonS3Client(accessKey, secretKey, mRegionEndpoint);
        string s3MediaUrl = UploadFileToS3(inputAudioFilePath, s3BucketName, s3KeyName);
        string ext = Path.GetExtension(inputAudioFilePath).ToUpper();
        MediaFormat mediaFormat = MediaFormat.Wav;
        if (String.Compare(ext, ".MP3", true) == 0)
            mediaFormat = MediaFormat.Mp3;

        #endregion

        var media = new Media() { MediaFileUri = s3MediaUrl };
        var request = new StartTranscriptionJobRequest
        {
            TranscriptionJobName = jobName,
            LanguageCode = inputLanguage,
            Media = media,
            MediaFormat = MediaFormat.Mp3,
        };

        try
        {
            string text = "";
            StartTranscriptionJobResponse response = client.StartTranscriptionJob(request);
            if (response.HttpStatusCode == System.Net.HttpStatusCode.OK)
            {
                Console.WriteLine("Transcription completed successfully");

                if (response.TranscriptionJob.Transcript != null && response.TranscriptionJob.Transcript.TranscriptFileUri != null)
                {
                    string transcriptUrl = response.TranscriptionJob.Transcript.TranscriptFileUri.ToString();
                    WebClient webClient = new WebClient();

                    string targetDir = Path.Combine(Program.InstallDir, @"TTSExperiment\Transcribed");
                    if (!Directory.Exists(targetDir))
                    {
                        Directory.CreateDirectory(targetDir);
                    }
                    string localFilePath = Path.Combine(targetDir, Path.GetFileNameWithoutExtension(transcriptUrl) +".txt");
                
                    webClient.DownloadFile(transcriptUrl, localFilePath);

                    text = File.ReadAllText(localFilePath);

                    Console.WriteLine($"Transcription job {jobName} completed.");
                }
                else
                {
                    Console.WriteLine("No Transcript created");
                }
                return text;
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error starting transcription job: {ex.Message}");
        }

        return "";
    }

Your colleague is correct, you do need to poll for results or check some other way, because transcriptions can take a very long time depending on the length of the media. The AWS SDK examples repository includes a .NET example that uses some simple polling logic that you may find useful.

Console.WriteLine("Start a transcription.");

    var transcriptionName = $"ExampleTranscription_{DateTime.Now.Ticks}";

    var transcriptionJob = await transcribeWrapper.StartTranscriptionJob(
        transcriptionName, transcriptionMediaLocation, MediaFormat.Mp3,
        LanguageCode.EnUS, null);

    Console.WriteLine($"Transcription started: {transcriptionJob.TranscriptionJobName}, " +
                      $"status: {transcriptionJob.TranscriptionJobStatus}.");

    Console.WriteLine($"Waiting for transcription {transcriptionName}.");

    while (transcriptionJob.TranscriptionJobStatus != TranscriptionJobStatus.COMPLETED
           && transcriptionJob.TranscriptionJobStatus != TranscriptionJobStatus.FAILED)
    {
        transcriptionJob =
            await transcribeWrapper.GetTranscriptionJob(transcriptionName);
        Thread.Sleep(5000);
    }

    Console.WriteLine($"Transcription status:  {transcriptionJob.TranscriptionJobStatus}, " +
                      $"completed at: {transcriptionJob.CompletionTime}.");