Case Study
PayLoop
Overview
PayLoop is a backend service for tracking recurring subscriptions and reminding people before they renew. It exposes a REST API for accounts, subscriptions and renewal schedules.
The Problem
Subscriptions are easy to start and easy to forget. Spread across cards, apps and currencies, renewals tend to arrive as surprises — usually after the charge has gone through.
Our Approach
Adding a subscription starts a durable workflow on Upstash that emails reminders seven, five, two and one day before renewal, and stops on its own once the subscription is no longer active. Subscriptions can be tracked in USD, EUR, GBP or INR, across cards, PayPal and bank transfer.
Architecture & Features
The API is Node.js and Express on MongoDB via Mongoose, with Day.js for date arithmetic. Authentication uses JWTs with bcrypt-hashed passwords, and requests pass through Arcjet for rate limiting, bot detection and shield protection. Reminders go out through Nodemailer. PayLoop is API-only: it's deployed on Render and documented for integration, and has no end-user interface of its own.
Role
Backend, API design, Security
Related services
Technology
Node.js, Express, MongoDB, Upstash Workflow, Arcjet, Nodemailer