This tutorial provides a comprehensive guide to building an SMS reminder system using Node.js, Express, and the Infobip API. You'll learn how to set up the project, handle API requests, schedule reminders, and send SMS notifications reliably. The system uses node-cron for scheduling and offers options for persistent storage with SQLite or an in-memory store for simplicity.

The Infobip SMS API is the core communication component of the reminder system. It's used to send the actual SMS messages to users at the scheduled time. The Infobip Node.js SDK simplifies interaction with the API, handling authentication and requests.

Node-cron is a task scheduler for Node.js that allows you to define tasks to run at specific intervals, similar to cron jobs. This is essential for checking the database or in-memory store periodically for reminders that are due to be sent.

SQLite is recommended for production environments or any scenario where data persistence is required. If the server restarts, reminders stored in SQLite will be preserved, unlike the in-memory option where data is lost on restart.

While the tutorial uses SQLite as an example for persistent storage, you can adapt it to other databases. The core logic for interacting with the database is encapsulated in the reminderService.js file, allowing for flexibility in database choice.

You'll need an active Infobip account. The API key and base URL can be found in your Infobip portal. Create a .env file in your project's root directory and store these credentials there. Ensure the .env file is added to your .gitignore to prevent it from being committed to version control.

Express-validator is used to validate incoming API requests, ensuring that required fields like phone number, message, and schedule time are present and in the correct format. This adds robustness and security to the system.

The tutorial provides a basic regex for E.164 phone number format validation. For more comprehensive validation, consider using a specialized library like libphonenumber-js which can handle various international phone number formats and validation rules.

You should have Node.js and npm (or yarn) installed. An active Infobip account and API key are required. A basic understanding of REST APIs, asynchronous programming, and JavaScript is also recommended.

The project demonstrates basic error handling, including checking for configuration errors, catching database issues, logging Infobip API errors, and using a global error handler in Express to catch and format errors for appropriate responses.

Once the server is running, you can use tools like Postman or curl to send test requests to the API endpoint (/api/reminders). These tools allow you to send POST requests with the required data (phone number, message, and schedule time) and examine the responses.

After setting up the project, use npm start to run the application in production mode. For development, use npm run dev which automatically restarts the server whenever you make changes to the code. This requires installing nodemon as a development dependency.

The diagram illustrates the flow of data and interactions within the reminder system. It visually represents how client requests flow through the API, interact with the services, and eventually send messages via the Infobip API.

The project uses Node.js with Express for building the backend API and handling requests. Infobip's SMS API and Node.js SDK handle messaging, while node-cron schedules tasks. SQLite provides optional persistent storage, and express-validator manages request validation.

Storing schedule times in UTC (using toISOString()) ensures consistency and avoids issues related to time zones. This is especially important in reminder systems to ensure that messages are sent at the correct time, regardless of the server's location or the user's time zone.