Sergio Xalambrí

Experience

1. 2021 – Present

   Web Developer · Daffy (formerly Silverback Ventures)

   • Build the web app of Daffy, a donor-advised fund that grew into a top-10 DAF in the U.S. with more than 16,000 accounts.
   • Migrated the app from Next.js to Remix in nine months with no feature freeze, running both in one server with shared sessions while routes moved over one at a time.
   • Designed a Remix backend-for-frontend over the Rails API, with a schema-validated API client, generated PDF donation reports and Open Graph images.
   • Extracted the patterns into Remix Utils, Remix Auth strategies and remix-i18next, now open-source libraries other teams build on.
2. 2018 – 2021

   Frontend Lead · Able

   • Led the frontend architecture of an internal product being prepared for public launch, building with React against a Rails backend.
   • Wrote the initial frontend curriculum for Codeable, Able’s full-stack bootcamp, and taught its React course.
3. 2017 – 2018

   Support Engineer · ZEIT (now Vercel)

   • Helped customers deploy to Now and adopt Next.js, building sample apps for their use cases.
   • Worked on the documentation of ZEIT’s API, so customers could learn the platform without a support ticket.
4. 2015 – 2017

   Frontend Developer · Platzi

   • Built the live classes system, discussions, the video player and React server rendering on the Django platform of a YC-backed online school.
   • Open-sourced Pulse Editor, Platzi’s Markdown editor, and Pulse, its Electron desktop app; taught web development courses.

Open source

• Remix UtilsUtilities for routes, responses, server-sent events, CSRF and more.1.6M downloads a month, 2.3k stars
• Remix AuthAuthentication for Remix and React Router apps, with dozens of strategies.650k downloads a month, 2.2k stars
• remix-i18nextTranslations for Remix and React Router apps with i18next.700k downloads a month
• The @sdxc packages130+ packages and a CLI for full-stack apps on Web Platform APIs and Cloudflare Workers.
• ContributorRemix, React Router, Next.js, SWR and micro.

Figures from GitHub and npm, October 2026.

Talks and writing

• The Remix Way · Remix Jam 2026, Toronto2026
• Remixing How We Give · Remix Conf Europe 20222022
• Hundreds of articles and tutorials · sergiodxa.com2013 – Present

Skills

Languages and frameworks

TypeScript, JavaScript, React, Remix, React Router, Next.js, Node.js, Bun

Platform

Cloudflare Workers, D1, KV, Durable Objects, Express, Rails APIs, SQL

Practices

Authentication (OAuth 2.0, OpenID Connect, passkeys), testing with Vitest, accessibility, progressive enhancement, library and API design, technical writing