Xavier Perez / Senior Full-Stack Product Engineer
From complex problems
to products people use.
I help founders and product teams build, improve, and ship software. Product judgment, thoughtful interfaces, and hands-on engineering across the stack.
100%
Job Success
15,309
hours on Upwork
Top Rated
Plus on Upwork
Profile checked September 20, 2026
Featured product story
Product strategy · Experience · Full-stack engineering
Armonía
From practice research to a system used every day.
An end-to-end product system for a psychology practice, shaped from discovery through daily operations and public distribution.
Explore the product story
The client portfolio
Different challenges.
The same commitment.
28 engagements across web, mobile, cloud, and testing. Explore the work that matches what your product needs next.
THE TECHNOLOGY
React
Next.js
MongoDB
APPLICATION / CLOUD / DATA
Full stack & cloud
2023 · work delivered
One engineering partner. Across the stack.
Frontend and backend delivery with React, Next.js, MongoDB, and AWS. The work is delivered; the Upwork contract remains open.
Full-stack product engineer
THE TECHNOLOGY
React
Next.js
INTERFACES / APPLICATION STATE
Full stack & cloud
2022 - 2023
Senior React expertise. Dependable delivery.
Senior React and Next.js development for a remote full-stack engagement, completed on time according to the client.
Senior full-stack developer
THE TECHNOLOGY
React
Next.js
MUI v5
DATA / CONNECTED WORKFLOWS
Web & product
2022
Interactive tools for a world of research.
React, Next.js, MUI v5, and Firebase development for an academic research platform.
React & Next.js developer
THE TECHNOLOGY
React
Cypress
Nx
TEST / VERIFY / DELIVER
Testing & reliability
2022
Tests that reach beyond the interface.
I improved unit and integration tests by bringing backend-service emulators into the test process.
Test automation engineer
THE TECHNOLOGY
React
Cypress
Nx
TEST / VERIFY / DELIVER
Testing & reliability
2021 - 2022
A stronger foundation for every release.
I started Cypress end-to-end testing for a new React product and established practices the team could continue using.
Cypress test automation developer
THE TECHNOLOGY
React
INTERFACES / APPLICATION STATE
Web & product
2021 - 2022
React interfaces, down to the details.
Senior React support for responsive interfaces, cross-browser behavior, and precise UI implementation.
Senior React developer
THE TECHNOLOGY
Node.js
React
APPLICATION / CLOUD / DATA
Full stack & cloud
2021
Connecting the interface to login automation.
A Node.js login-automation application with a React frontend.
Node.js & React developer
THE TECHNOLOGY
React
INTERFACES / APPLICATION STATE
Web & product
2020 - 2022
React interfaces for the long run.
React frontend development for a web application, under the October 2020 to August 2022 contract.
React frontend developer
THE TECHNOLOGY
React
IDEA / INTERFACE / PRODUCT
Web & product
2020 - 2021
From a Google Doc to a working prototype.
I helped a remote team turn early ideas into a working frontend prototype for a predictive diagnostics product.
Frontend product developer
THE TECHNOLOGY
React
IDEA / INTERFACE / PRODUCT
Web & product
2020
Frontend foundations for a gaming marketplace.
React frontend and integration work for a marketplace serving the online gaming community.
React frontend developer
THE TECHNOLOGY
React
Redux
INTERFACES / APPLICATION STATE
Web & product
2020
React and Redux, built to evolve.
I developed a React and Redux application with attention to UX, modular code, and tests.
React & Redux developer
THE TECHNOLOGY
React
INTERFACES / APPLICATION STATE
Web & product
2019
Design intent, brought to life in React.
I brought product interface designs to life in React, with the client recognizing the accuracy of the finished screens.
React interface engineer
THE TECHNOLOGY
React
INTERFACES / APPLICATION STATE
Web & product
2019 - 2020
Code the next engineer can build on.
I developed maintainable React code for Slicify and gave the team direct feedback on product ideas.
React application developer
THE TECHNOLOGY
React Native
MOBILE / CROSS-PLATFORM
Mobile
2019
React Native for an ambitious product team.
A brief React Native engagement for a startup building a graph-based AI application.
React Native developer
THE TECHNOLOGY
React
React Native
Node.js
TEST / VERIFY / DELIVER
Testing & reliability
2019
Find the crash. Fix the whole picture.
I diagnosed a crash and repaired the React website and Node.js server, with related changes to the React Native app.
Full-stack troubleshooting engineer
THE TECHNOLOGY
React
Redux
APPLICATION / CLOUD / DATA
Full stack & cloud
2019
React interfaces. Predictable application state.
A full-stack web application engagement centered on React and Redux.
React & Redux full-stack developer
THE TECHNOLOGY
Node.js
React
Relay
APPLICATION / CLOUD / DATA
Full stack & cloud
2018
An established product. Immediate contribution.
I joined an established Node.js application team and contributed using React, Relay, and GraphQL.
Full-stack web developer
THE TECHNOLOGY
React
IDEA / INTERFACE / PRODUCT
Web & product
2018
React engineering for an AI team.
React frontend development for an AI company.
React frontend developer
THE ENGAGEMENT
Mobile development
Existing product context
MOBILE / CROSS-PLATFORM
Mobile
2017 - 2018
Focused engineering for a mobile product.
A focused mobile application development engagement recorded between October 2017 and January 2018.
Mobile application developer
THE TECHNOLOGY
React Native
TEST / VERIFY / DELIVER
Testing & reliability
2017
An inherited app. A build that works.
I helped a server-side development team resolve a build issue in an inherited React Native application.
React Native troubleshooting developer
THE ENGAGEMENT
Catalog development
Repeat collaboration
DATA / CONNECTED WORKFLOWS
Data & workflows
2017
Keep a catalog product moving forward.
Further development on a catalog application during an August to September 2017 engagement.
Catalog application developer
THE ENGAGEMENT
Login functionality
Import & export
DATA / CONNECTED WORKFLOWS
Data & workflows
2017
Bring access and catalog workflows together.
Login and import/export functionality for a catalog application.
Catalog application developer
THE TECHNOLOGY
Node.js
Linux
MOBILE / CROSS-PLATFORM
Mobile
2017 - 2018
Wallet engineering across web and mobile.
I contributed across frontend and backend work for web and mobile wallet applications.
Web & mobile full-stack developer
THE ENGAGEMENT
Bug investigation
Database research
DATA / CONNECTED WORKFLOWS
Data & workflows
2017
Untangle the bugs. Understand the data.
Bug fixes and database research for UR money.
Application maintenance developer
THE TECHNOLOGY
React
DATA / CONNECTED WORKFLOWS
Web & product
2017
Complex information. A usable React dashboard.
I collaborated with the client's team to deliver a React desktop dashboard application.
React dashboard developer
THE ENGAGEMENT
Application corrections
Mobile maintenance
MOBILE / CROSS-PLATFORM
Mobile
2017
The next round of mobile improvements.
Mobile application corrections during the March 30 to May 12, 2017 contract.
Mobile application developer
THE ENGAGEMENT
Mobile corrections
Existing application
MOBILE / CROSS-PLATFORM
Mobile
2017
Focused fixes for an existing mobile app.
A short mobile application corrections engagement from March 27 to March 29, 2017.
Mobile application developer
THE TECHNOLOGY
Ionic
TypeScript
Node.js
MOBILE / CROSS-PLATFORM
Mobile
2016 - 2017
My first Upwork project. An app brought to life.
My first Upwork project: helping create and launch an Ionic mobile application.
Ionic mobile developer
Your next project
Bring me the hard part.
Let’s work out what’s next.
A new product, a stalled release, or a system that needs a stronger foundation. Tell me where you are and where you want to go.