Digital product · Design · Build
Northstar
A private investing platform. Savings, funds and crypto in a single quiet view, priced against live market data, with written rules and a weekly letter. The public demo runs the same software on sample data.
The work
Built for numbers
someone has to trust.
Northstar gathers a whole portfolio into one quiet view: savings, funds, shares and crypto, each priced against live market data, so the figure on screen is the figure that is true today. The discipline is written into the product itself: nothing gets bought without a written case and a waiting period, alert levels do the watching, and a weekly letter reports what actually happened.
The care is in the plumbing. The platform is read-only by design: the code can ask what a holding is worth, but no code exists that can move money. The rules that keep the numbers honest live in the database itself, and every sum that touches money is covered by tests, the tax workings most of all.
In July 2026, Real Vision had John on their live AI show, The World According to AI, to talk about the platform. The demo linked below is the version shown there: the same software, running entirely on sample data. If your business runs on numbers someone has to trust, this is what that looks like.
Product design
The screens, the words, and a quiet way of reading numbers. Designed for one careful reader.
Full build
Next.js, TypeScript and Supabase, hosted in Europe, with tests on every sum that touches money.
Live market data
Funds, shares and crypto priced against live feeds, arriving through one governed door.
Built-in discipline
Written cases, waiting periods and alert levels. The rules live in the product, not in good intentions.
