Design and Implementation Challenges in Multi-Payment Provider Gateway Integration : A Backend Developer Perspective

Abstract

This thesis examines the challenges of integrating multiple payment gateways into a single backend system. Currently, many applications require support for different geographical and worldwide payment methods. Still, each payment provider, Vipps, Paytrail, Stripe, and PayPal, has its own unique way of authenticating users, APIs created around them, and security measures taken while creating them. Solving this problem is vital for cross-regional systems that require safe and predictable workflows for handling payments. To address this problem, this thesis develops a modular backend architecture using Python Django and PostgreSQL. The system employs the Factory pattern to create and select payment providers consistently. This enables each payment gateway to operate independently while interfacing with a single API endpoint for initiating payments, verifying status, capturing payments, and issuing refunds. The multi-gateway backend also includes webhooks for real-time payment status updates, along with an MQTT solution to connect successful payments to a vending machine for unlocking the appropriate locker. Testing conducted within sandboxed environments confirmed that the unified backend architecture supported all four payment gateway providers while ensuring that the transaction flow was maintained consistently amongst each provider. The results of this research demonstrate that a modular, Factory-based approach provides a way to simplify multi-gateway payment systems and allows for a secure, scalable implementation of integration into those payment systems.