🚀 Building a Paytm Clone: Architecture, Security & Scalability Insights

In my latest project, I set out to recreate the core functionality of Paytm — allowing users to add money, send money, and manage their wallet — but with a backend architecture and deployment pipeline modeled for real-world scale, security, and resilience.

The frontend is powered by Next.js, designed as a user-facing application. I used NextAuth for authentication, which securely manages user sessions without relying on localStorage — everything is handled server-side through HTTP-only cookies, reducing session hijacking risks.

To simulate a banking system securely, I implemented a webhook that acts as a trusted channel between the bank and the app. The bank hits this endpoint with a secure token whenever money is added to the user’s wallet. It’s isolated from the main API to prevent unauthorized access and to avoid abuse.

To handle concurrency, I used row-level locking to block multiple threads from modifying the same balance simultaneously. This ensures transactional safety, preventing double-spending or race conditions during wallet-to-wallet transfers.

The app was containerized with Docker and deployed using a CI/CD pipeline set up through Docker Hub. Each change pushed to GitHub triggers a build and deployment to a Google Cloud e2 instance via Compute Engine. This automated flow minimizes downtime and human error, making deployment fast and reliable.

What started as a simple Paytm clone evolved into a deeply educational journey into system design, DevOps, authentication security, and distributed computing. It's a solid foundation for building real-world fintech systems that need to be secure, scalable, and user-friendly.

Built with ❤️ using Next.js and styled to match Excalidraw's sketchy aesthetic.