Building a Serverless Appointment Scheduler Using Twilio, Express, and AWS: Initial Configuration

6 min readMay 15, 2024

a Phone Interaction Interface: A creative depiction of a phone interface with various interaction options, such as a touchpad for DTMF tones or a speech bubble for voice commands. This image could visually represent how users might interact with the scheduling system via their phone, emphasizing user engagement and technology interface

Setting up a phone number for clients to schedule meetings is straightforward with the right tools. This guide uses Twilio for phone number management and AWS for hosting in a Serverless Architecture. For local development and testing, we’ll use Express and ngrok.

Setting up Express and Running It:

To interact with Twilio using Express:

Initialize a new project: npm init — yes
Install necessary packages: npm install — save express twilio body-parser
Create index.js with the following basic server setup:

const express = require('express');
const bodyParser = require('body-parser');
const app = express();
app.use(bodyParser.urlencoded({ extended: false }));

app.get('/hello', (req, res) => res.send('Hello World!'));

app.listen(3000, () => {
  console.log('Express server running on port 3000');
});

4. Start the server: node index.js

For a smoother development experience, use nodemon to automatically restart the server after changes:

npm install -g nodemon
nodemon index.js

Making Your Local Service Globally Accessible with ngrok:

Ngrok exposes your local server to the internet by mapping a public HTTP endpoint to your local port.

Sign up and download ngrok from ngrok.com.
Set up ngrok and authenticate with your account.
Start ngrok to expose port 3000: ngrok http 3000
Note the ngrok URL provided; this will be used as your webhook URL.

Setting Up Twilio:

Purchase a phone number through Twilio’s dashboard.

2. Set up a webhook URL in Twilio to point to the ngrok URL, enabling Twilio to send requests to your local server.

Setting Up Twilio JS SDK to Say “Hello World”:

Update your Express application to respond with Twilio’s TwiML, which instructs Twilio on what to do with calls:

const { VoiceResponse } = require('twilio').twiml;

app.all('/', (req, res) => {
  res.type('xml');
  const twiml = new VoiceResponse();
  twiml.say("Welcome to your calendar");
  res.send(twiml.toString());
});

This setup creates a basic phone number that can interact with clients and is a starting point for more complex scheduling functionalities. As the application stabilizes, transition from ngrok to AWS for a more robust Serverless Architecture.

Testing Your Twilio Setup:

Once your setup is complete with Express, ngrok, and Twilio, it’s important to test and ensure everything functions as expected. This testing involves making a call to your newly purchased Twilio phone number and verifying that the system responds correctly.

Steps to Test Your Phone System:

1. Call the Twilio Number: Use any phone to dial the number you purchased from Twilio.

2. Listen for the Response: When the call connects, you should hear the voice message: “Welcome to your calendar.” This confirms that your Twilio setup is correctly handling incoming calls and that your Express application is responding with the appropriate TwiML commands.

3. Check the Logs: If the voice message doesn’t play, check your Express server and ngrok logs for any errors. The logs can provide insights into what might be going wrong, such as connectivity issues or incorrect request handling.

4. Debugging Tips:

• Ensure that your local server is running and accessible via ngrok.

• Verify that the webhook URL in your Twilio configuration matches the ngrok URL.

• Confirm that there are no syntax errors in your Express application that might prevent it from sending the correct TwiML response.

5. Iterate: If you encounter issues, make the necessary adjustments in your setup or code, and test again. It’s often a process of trial and error to get everything working smoothly.

What’s Next?

In this article, we’ve covered how to set up a basic phone number with Twilio, run an Express server, and make your local development environment accessible globally using ngrok. We also walked through the initial testing to ensure that your system can handle a basic interaction — responding with a voice message when your Twilio number is called.

Upcoming Article: Handling User Interactions

Stay tuned for the next article where we will dive deeper into enhancing your scheduling system. We’ll explore how to handle more complex user interactions, such as:

• Receiving Input from Users: How to gather and process user input via keypad (DTMF tones) or voice during the call.

• Dynamic Responses: Implementing logic to respond differently based on the user’s input or time of the call.

• Scheduling Logic: Integrating a calendar or scheduling API to allow real-time appointment setting and modifications.

• Persisting Data: Storing user data and interaction logs securely using AWS services.

The upcoming guide will provide step-by-step instructions to evolve your simple phone system into a fully interactive appointment scheduler. This will include coding examples, best practices, and tips on maintaining and scaling your system.

Be sure to follow this series to transform your service into a powerful tool that enhances your customer’s experience and streamlines your scheduling process.

This wrap-up not only summarizes what has been covered but also generates interest in the forthcoming content, encouraging readers to follow the series for more in-depth development tutorials. If you need any more tweaks or additional content, feel free to let me know!

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