PayPlan
full-stack
fastapi
react
aws
A payment-plan simulator with idempotent sandbox checkout, deployed on AWS with monitoring.
Overview
PayPlan lets users compare installment dates, total costs and remaining balances before they check out. A React front end talks to object-oriented Python services exposed through documented FastAPI endpoints.
Making payments safe to retry
Payment code has to handle retries, double-clicks and network failures without charging twice. PayPlan prevents duplicate sandbox payments with three layers:
- Idempotency keys on every checkout request
- Unique database constraints as a backstop
- Atomic transactions so a payment and its records commit together or not at all
48 automated pytest cases cover concurrency, rounding and retry behaviour.
Deployment and monitoring
GitHub Actions deploys the frontend and API automatically:
- API on AWS ECS Fargate with RDS (PostgreSQL)
- Frontend on S3 + CloudFront
- CloudWatch tracking errors and latency after each release
Stack
Python · FastAPI · React · TypeScript · PostgreSQL · AWS