About - Franklin Javier

I’m Franklin Javier, a Principal Engineer. I’ve been doing front-end since 2007, on high-performance web and mobile apps, and today I lead front-end and agentic engineering work across product teams.

These days almost everything I do involves AI. I build harnesses and orchestration for coding agents across Claude Code, Cursor, Codex and Gemini CLI: the skills, evals and guardrails that make an agent reliable enough to ship with. This site follows the same idea: every page has a markdown version, served through content negotiation, plus an llms.txt guide, so agents can read it as well as a browser can.

Beyond that, I work on React and Node.js architecture, web performance and observability, design systems and accessibility (a11y). Day to day I use React, TypeScript, React Router, Remix, Node.js, Tailwind CSS, Drizzle and Postgres, plus the Vercel AI SDK, Playwright and Vitest.

Experience

Principal Engineer at Stone Giant Studio (2023 - Present), home of Erastus, practice management software for architecture and engineering firms that puts timesheets, time off, staffing, project scheduling and profitability in one place, with payroll and accounting integrations, now with over 1,500 registered users
Principal Engineer at Grupo Boticário (2021 - 2023)
Sr Digital Product Manager at Grupo Boticário (2020)
Head of Technology at Beleza na Web (2015 - 2020)

The full history is on the CV.

Side projects

Zelus: condominium management, with issue tracking and an AI assistant grounded in the condominium’s data
Project Campfire: pulls tasks, decisions and deadlines out of conversations, with owners, due dates and a trail back to the source
Robot Loupe: human-in-the-loop review for AI-generated database changes, checking impact and standards before they ship

Open source

I publish a lot of my work as open source, including AI projects. Most recently stonegiantstudio/skills, a set of Apache-2.0 skills for AI coding agents, portable across Claude Code, Cursor, Codex and Gemini CLI.

Older and still in production: storefront, the Node.js and Redis boilerplate we standardised on for e-commerce. It runs the Beleza na Web and Grupo Boticário storefronts, and holds over 1M requests per minute. My other repositories are at github.com/franklinjavier.

I’m based in Lisbon, Portugal, and I write on this site in both English and Portuguese about front-end development, React, performance, and engineering culture. You can read my articles on the blog, read my CV, or get in touch.