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Serverless form submission via AWS Lambda to Slack channel
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Serverless form submission via AWS Lambda to Slack channel


Before deploying serverless backend for a web from you need

  1. Google reCAPTCHA
    Register yoursite for Google reCAPTCHA and get your site key and secret key.

  2. Slack webhook for posting the form to a Slack channel
    Register Slack workspace and create an incoming webhook for posting to a channel

  3. (optional) Route53 zone for a custom name for the backend

  4. (optional) ACM certificate at us-west-1 to match your custom name

If you don't want to have custom name, leave both 3 & 4 empty and you will get standard name


Once you have all above preparations done

  1. Build Cloudformation stack with feedbackapi.yaml -template
    Template will take 5 parameters
  • APIStage is just a name for your API stage. You can leave it as default "prod" or call it whatever you want.
  • ReCaptchaSecret is the SECRET key you got when registered your site to Google reCAPTCHA.
  • Webhook is URL of webhook for posting to Slack channel.
  • CustomDomain is optional parameter. If you have Route53 domain you can register a custom name for the API Gateway backend. Full name of your API will be STACKNAME.CustomDomain, e.g.
  • CustomCert is optional parameter. If you supplied CustomDomain this must be an ARN of matching ACM certificate at us-east-1 -region. Stack itself can be built into any region you choose.

    Once stack is ready, you will find the URL of API in stack outputs.
  1. Modify feedback.html -sample form
    Replace __reCaptchaSitekey__ and https://URL/TO/YOUR/AWS/APIGW/ with real values you obtained earlier.
          <button type="submit" class="g-recaptcha form__button"

  <script src='' async defer></script>
    var handleFormSubmit = function () {
      var formApiEndpoint = "https://URL/TO/YOUR/AWS/APIGW/"
      var successEl = document.querySelector('.form__success')
  1. Open feedback.html in your browser and submit the form to your Slack channel!
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