eSIM Sales Platform

An eSIM e-commerce platform built at ComDigital for instant purchase and payment.

Problem and purpose

Customers buy and pay for eSIMs instantly, many purchases can arrive at the same time, and external eSIM and payment services can fail. An order must never charge or provision twice.

My role and responsibility

I built the platform at ComDigital: the high-concurrency FastAPI backend and the Next.js and Nuxt.js frontends, integrated with external eSIM and payment services.

Architecture and key decisions

• Idempotent order and payment handling, so a retried request or a repeated callback never charges or provisions twice
• Concurrency control on orders and stock when many purchases arrive together
• Compensation steps when an external call fails after payment, so every order ends in a consistent state
• Audit logging of every order, payment and provider event
• Response times and error rates of the purchase flow are measured in production on the Kubernetes, Graylog and Grafana platform

Technologies

Python (FastAPI), Next.js, Nuxt.js, Docker, Kubernetes.