Case study · 2026 · Live
RetireCheck
RetireCheck is a production retirement planning tool: a four-step wizard, animated score gauge, Monte Carlo fan chart, SSA FRA lookup, and shareable results. Built as a monorepo with a Next.js frontend, ASP.NET Core API, and pure C# domain engine — deployed on Vercel and Render.
What it does
RetireCheck walks users through a four-step retirement planning wizard and returns estimates for Social Security claiming, tax and RMD projections, and Monte Carlo portfolio outcomes — with clear disclaimers that results are estimates, not advice.
Architecture
Financial math lives in a pure C# domain layer. The Next.js frontend proxies to an ASP.NET Core API. That separation keeps the UI fast to iterate while protecting calculation correctness behind automated tests.
Product surface
- Four-step planning wizard with progressive inputs
- Animated score gauge and shareable results summary
- Monte Carlo fan chart for portfolio outcome ranges
- SSA FRA lookup and tax / RMD projection context
How it was built
RetireCheck is also the flagship case for the AI in Action series: Cursor accelerated UI and scaffolding, while domain boundaries, tests, and production judgment stayed engineer-owned. Read the full write-up in AI in Action: Building RetireCheck with Cursor.
Stack
- Next.js 16, TypeScript, Tailwind, Recharts
- ASP.NET Core Web API + RetirementCalculator.Domain
- xUnit domain and API tests
- Vercel (frontend) + Render (API)