Payment & Affiliate Services

I developed and maintained backend services that powered App For Language (FunFluen)'s payment and affiliate infrastructure using FastAPI, MongoDB, Redis, and Stripe.

The payment service centralized Stripe interactions such as customer creation, checkout sessions, subscription management, and webhook processing, while persisting subscription state in MongoDB for other services to consume.

The affiliate service handled referral links, click tracking, sign-up and purchase attribution, and commission logic. It integrated with the payment flow through Stripe customer metadata and webhook events, allowing referral statistics to be updated without polling.

Together, the services used centralized JWT authentication, Redis-based rate limiting, webhook-driven workflows, and Dockerized deployment as part of a multi-service backend architecture.

• Built a layered FastAPI payment service that abstracted Stripe SDK operations behind reusable service-level functions.
• Implemented secure checkout and API authentication using cookie-based token refresh flows and header-based JWT authentication.
• Implemented Stripe webhook processing with signature verification and idempotent event handling for subscription and payment-related events.
• Built an affiliate backend for referral links, click tracking, sign-up and purchase attribution, and automated commission calculations.
• Connected affiliate attribution to the payment flow by storing affiliate codes in Stripe customer metadata and processing Stripe webhook events.
• Implemented Redis-based rate limiting for referral clicks to reduce bot and click-spam abuse.
• Used MongoDB for persistent payment and affiliate data and Redis for caching and rate-limiting workloads.
• Dockerized the services and their database environments for predictable development and deployment.

Payment Service

Internal payment infrastructure for Stripe customer management, checkout sessions, subscription management, and webhook processing.

Affiliate Service