I build software that handles money. I care most about keeping the numbers right when requests are retried, arrive out of order, or race each other.
Building Countorra: a personal finance and tax app, in development, not launched yet. It connects to banks through Plaid and handles subscriptions and checkout through Stripe. It calculates tax figures for the 2026 US federal rules and supported states. An assistant answers questions from your own records. Built with Next.js, TypeScript, Postgres (Supabase) and row-level security.
| Repo | The problem it solves |
|---|---|
| ledger-invariants | A double-entry ledger where Postgres refuses unbalanced entries, edits to history, double posting and overdrafts. Tested under real concurrency. |
| idempotency-keys | Stripe-style idempotency keys for your own API. Tested by crashing a request at every step, so a retry never charges twice. |
| stripe-entitlements | Correct subscription access from Stripe webhooks, whatever order they arrive in. |
| stripe-price-guard | A CI check that refuses a production build when live Stripe prices don't match what the site charges. |
Depending on the repo, the tests use property-based testing, fault injection, and concurrency tests on a real Postgres server.
Open to software engineering internships · San Jose, CA