Use RedwoodJS's full-stack framework along with Infobip's SMS API and Node.js for scheduling. The application allows users to schedule appointments through a web interface, and the system automatically sends SMS reminders at the designated times, handling time zones correctly.

RedwoodJS is the core framework for building both the frontend (using React) and the backend (GraphQL API) of the SMS scheduling application. It provides structure, conventions, and developer-friendly features like generators and cells.

Infobip is a CPaaS provider offering a robust SMS API and a convenient Node.js SDK, making it straightforward to integrate SMS sending functionality into the application. Their platform is designed for reliable message delivery.

Use date-fns-tz for accurate timezone conversions, especially when scheduling tasks. It's crucial for ensuring that SMS reminders are sent at the correct local time for recipients in different time zones and for handling daylight saving time.

Install the Infobip Node.js SDK (@infobip-api/sdk) and configure your API key and base URL in the .env file. Then create a service to interact with the Infobip API using the SDK to send SMS messages.

PostgreSQL is used as the database to store appointment details, recipient information, and message status. Prisma, an ORM, simplifies database interactions within the RedwoodJS application.

node-cron is a Node.js library that provides a simple way to schedule tasks using cron-like expressions. It's used to trigger SMS sending at the correct times, based on the scheduled time and the recipient's time zone.

Use date-fns-tz to calculate the correct cron expression based on the UTC scheduled time and the recipient's time zone. This will ensure that the SMS message is sent at the correct time for every user, regardless of their location.

Use the yarn create redwood-app command. Initialize a TypeScript project, configure your database connection in the .env file, and install necessary dependencies like the Infobip SDK, node-cron, date-fns-tz, and type definitions.

Prisma acts as an Object-Relational Mapper (ORM), simplifying database interactions. It allows you to define your data models and easily perform CRUD (Create, Read, Update, Delete) operations on your PostgreSQL database from your RedwoodJS backend.

Define your data model in the api/db/schema.prisma file. This file uses the Prisma schema language. Then run yarn rw prisma migrate dev to create and apply the migration to your development database.

Use the Infobip Node.js SDK in your API side. You will need your API key and base URL, available from your Infobip account dashboard. Provide the recipient's phone number and message text to the sendSms function.

Yes, update the appointment's details using an appropriate API call, including the new scheduled time and timezone if needed. The application will cancel any existing job and reschedule the SMS reminder based on the updated information.

You will need Node.js (version 20 or higher recommended), Yarn, an Infobip account, access to a PostgreSQL database, and basic familiarity with JavaScript/TypeScript, React, GraphQL, and terminal commands.