Use the Infobip API with the Node.js SDK and Express to create a system that can handle sending a single SMS message to many recipients. This guide provides a comprehensive walkthrough, explaining each step in detail, from project setup and core functions to error handling and deployment techniques. You'll build an Express application that accepts requests to send SMS messages to a large list of recipients via Infobip's bulk sending feature.

Use a tool like Postman to send POST requests to the `/api/v1/broadcasts` endpoint. Include a JSON body with the `message` and an array of `recipients`. Alternatively, you can omit `recipients` to send to all active recipients in the database.

Infobip is a cloud communications platform offering APIs for various channels like SMS, voice, and chat apps. Its robust SMS API, accessible via the official Node.js SDK, is ideal for sending large volumes of SMS messages reliably and quickly. This guide utilizes Infobip for broadcasting alerts, information, or marketing messages.

Start by creating a new directory, initializing a Node.js project with `npm init -y`, and installing necessary dependencies like `express`, `@infobip-api/sdk`, `dotenv`, `pg`, `@prisma/client`, and development dependencies including `prisma`, `nodemon`, `jest`, and `supertest`. Structure your project with directories for controllers, routes, services, utils, middleware, and tests.

The guide utilizes PostgreSQL as its relational database and Prisma as an ORM for database interactions. However, the core concepts can be adapted to other ORMs supported by Prisma (like TypeORM, Sequelize) or databases (e.g., MySQL, MariaDB) with necessary code modifications. Remember to configure your database credentials in the .env file.

The Infobip Node.js SDK simplifies interaction with the Infobip API. It handles authentication, request formatting, and response parsing, making it easier to integrate Infobip services into your Node.js application. The SDK is initialized with your Infobip Base URL and API key, which are stored as environment variables for security.

Store your `INFOBIP_BASE_URL` and `INFOBIP_API_KEY` in a `.env` file. This file should be added to your `.gitignore` to prevent it from being committed to version control. While suitable for development, for production environments, inject environment variables directly through your hosting platform or CI/CD pipeline for enhanced security.

Prisma acts as an Object-Relational Mapper (ORM), simplifying database interactions. It allows you to define your database schema using the Prisma Schema Language in `schema.prisma` and interact with the database using JavaScript. This guide uses Prisma with PostgreSQL but can be adapted for other databases and ORMs.

Organize your project with a clear directory structure. This typically includes separate folders for controllers, routes, services, utils (like logging), and middleware. The `src/app.js` file handles the main Express application setup, while `server.js` serves as the entry point for starting the server.

Dotenv is a crucial package for managing environment variables, which hold sensitive information like API keys and database credentials. By loading these variables from a `.env` file, you keep them separate from your codebase, improving security. Remember to never commit the .env file to your repository.

Create a centralized error handler middleware that catches errors passed through `next(error)` and returns a structured error response. This simplifies error management and helps provide user-friendly error messages. Use try-catch blocks around async operations and log errors using a logger for debugging and tracking.

The guide provides a simple logger implementation using `console`. However, for production, libraries like `winston` or `pino` are recommended, offering more advanced logging features such as log levels, log rotation, and structured logging.

The system follows a client-server architecture: the client (e.g., Postman, UI) sends requests to the Node.js/Express API layer. The API layer interacts with both the Infobip service (via the Node.js SDK) and the PostgreSQL database (using Prisma). The Infobip service then communicates with the Infobip API to send the SMS messages.

The `sendBulkSms` function in the `infobipService.js` accepts an optional `sender` parameter. Pass your desired alphanumeric sender ID to this parameter when calling the function. Be sure to consult Infobip's rules regarding sender IDs to ensure compliance.

You need a free or paid Infobip account, Node.js and npm installed, access to a PostgreSQL database, and basic knowledge of Node.js, Express, APIs, and databases. For testing with a free trial, ensure you have a registered phone number linked to your Infobip account.