Sergio Castro Senior Software Engineer

I build polished mobile and web products with React Native, Expo, Flutter, React, Node.js, and TypeScript. Currently shipping scalable cross-platform apps at GlobalLogic .

6+

years shipping JavaScript products

3

platforms: web, iOS, and Android

TS

TypeScript-first product engineering

Selected Work

Built for real product pressure.

A focused snapshot of the systems, teams, and product surfaces I have helped move forward.

GlobalLogic

Enterprise Mobile Platforms

Building scalable cross-platform apps with React Native, Expo, and TypeScript for product teams that need native-quality delivery without doubling the codebase.

Impact: Reusable app architecture, cleaner feature delivery, and stronger mobile developer experience.

React Native Expo TypeScript Nativewind

Apex Systems

Modern React Application Upgrades

Modernized legacy React surfaces, routing flows, and UI architecture so teams could ship faster with less regression risk.

Impact: Improved maintainability across core user journeys and reduced friction for future feature work.

React React Router Testing Library Tailwind CSS

Pixelbot

Hume Health

Built mobile-centered health experiences in Flutter backed by Firebase and Express APIs so the product team could iterate quickly across iOS and Android.

Impact: Connected Flutter clients to Firebase-backed services and Node tooling without sacrificing release velocity.

Flutter Firebase Node.js Express

Pixelbot

Kaiber

Worked inside a Turborepo monorepo to ship typed React flows with nested routing alongside Express services and Mongoose-backed MongoDB persistence.

Impact: Faster experimentation on creative tooling through shared packages, strict TypeScript boundaries, and a cohesive data layer.

React React Router TypeScript Turborepo pnpm Node.js Express MongoDB Mongoose

Experience

A product engineer with range.

I am strongest where product detail, UI quality, and delivery discipline meet.

Mobile Engineer at GlobalLogic

Current

Shipping cross-platform mobile features with React Native, Expo, and TypeScript in a product environment that values scale and reliability.

Software Engineer at Apex Systems

Previous

Modernized React applications, navigation flows, and frontend foundations for more maintainable product delivery.

Full-Stack Developer at Pixelbot

Previous

Shipped Flutter mobile apps and Turborepo-based React tooling with Firebase, Express, MongoDB, and Mongoose-backed services.

Technical Strengths

Useful depth, not buzzwords.

Frontend & Mobile

React, React Router, React Native, Expo, Flutter, TypeScript, Tailwind CSS, Nativewind, responsive UI systems, and accessible interfaces.

Backend & Data

Node.js, Express, REST API design, Firebase, MongoDB and Mongoose, SQL and NoSQL persistence, Turborepo and pnpm monorepo workflows, and pragmatic system boundaries.

Quality & Delivery

Testing Library, clean architecture, practical refactoring, code review, maintainable abstractions, and reliable release habits.

Let's Build

Need someone who can own the interface and still understand the system behind it?

I am interested in teams building thoughtful products with React, React Native, Expo, Flutter, Node.js, and TypeScript.