Legacy-to-Expo migrations
Moving aging React Native codebases onto Expo and the new architecture without stopping product delivery.
Founder · WebNexus
João Paulo Marra
Staff/Principal React Native Engineer · Founder, WebNexus
João Paulo Marra is a Staff/Principal React Native engineer with 16+ years shipping mobile products — specializing in legacy-to-Expo migrations, C++ Nitro Modules, and zero-to-one mobile delivery.
Based in Goiânia, Brazil — working remotely across US and EMEA time zones.
Track record
Numbers behind the work.
Every figure below comes from shipped, production work — apps in the stores, code in front of real users.
90%
mobile engagement improvement from a legacy-to-Expo React Native modernization
~40%
better computational efficiency in critical paths of a production app via custom C++ Nitro Modules over JSI
30%
faster deployment cycles from release-engineering work — Expo EAS, OTA updates, Sentry
75%
technical-debt reduction through shared platform and component foundations
26 devs
led a healthcare modernization group at UnitedHealth Group (jQuery/Bootstrap → React) and built that business unit's first bare React Native app
16+ years
shipping production mobile and web products
Specialties
Where he does his best work.
C++ Nitro Modules & JSI
Custom native modules for hot paths — parsing, transforms, computation — off the JS thread, one C++ implementation for both platforms.
AI/LLM & RAG mobile features
LLM integrations, streaming chat UIs, and retrieval-augmented features built for mobile constraints.
Release engineering
Expo EAS pipelines, OTA updates, and Sentry observability — so shipping is routine, not an event.
Zero-to-one mobile delivery
First mobile hire territory: from empty repo to a published, maintainable app in the stores.
Team-scale modernization
Leading multi-developer groups through framework transitions while the product keeps moving.
Open source
Code in the open.
Writing
Notes from production.
When JavaScript Isn't Enough: Moving React Native Hot Paths to C++ with Nitro Modules
On this blog
The Road Less Bumpy: React Native's New Era of Stability and Predictability
On dev.to
Availability
He leads WebNexus, the engineering studio behind this site, and is open to Staff/Principal React Native and first-mobile-hire roles.