Joined as the first engineer to a freshly funded fintech. The product is a spreadsheet-shaped FP&A tool — financial planners live in it for hours a day — so the frontend has to survive datasets that crash a normal React grid in the first scroll.
What we picked
AG Grid Enterprise on the server-side row model. Most teams default to the client model and lose; SSRM streams chunks, the grid keeps a sliding window, and the tab stays responsive. CodeMirror 6 for formula cells, Recharts for dashboards, Editor.js for narrative commentary alongside the numbers.
What I owned end-to-end
Architecture, CI/CD, hiring loop, the Next.js app, plus enough of the Django backend to keep the schema honest. Set up the auth layer, the BI permissions model, and the deployment pipeline on day one so later engineers had a paved road.
What I'd do differently
Editor.js was the wrong call for the narrative block. We needed structured commenting more than rich text — a Slate schema or custom Prosemirror tree would have aged better.