Open to opportunities

Guillermo Pérez

@guillermoprez

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Senior full-stack engineer building scalable, high-performance JavaScript web apps with React, Next.js, and TypeScript.

Argentina

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What I'm looking for

I’m looking for a team that values performance, strong architecture, and great UX—where I can pair, keep code clean, and ship incremental, business-driven improvements in a modern JavaScript stack.

I’m a Senior Frontend & Full-Stack Engineer with 13+ years of experience building scalable web applications for US-based companies. I specialize in the modern JavaScript ecosystem—React, Next.js, TypeScript, and Node.js—focused on performance, architecture, and user experience.

I thrive in agile environments where I value clean code, pair programming, and delivering incremental, business-driven solutions. Across roles, I’ve partnered with Product Management to ideate features and proactively redesign critical UX flows, while also owning support escalations alongside sprint delivery.

In recent US startup work, I re-architected and launched an offline-first Progressive Web App (PWA) so field inspectors could operate seamlessly with no internet connection. I also owned end-to-end production deployment pipelines, managed service monitoring, and executed rapid system recoveries—while resolving complex legacy issues like cross-tab state contamination and context leaks that improved data integrity.

I’ve led engineering refactoring and platform integrations as well: I built a lead-management admin portal from scratch, refactored an internal project into market-ready quality by decoupling components and overhauling the design system, and drafted core architecture for Stripe integration to support subscriptions and add-on packages. Earlier, I acted as a Scrum Master (certified in 2022), maintained reliable unit/integration test suites, and helped teams accelerate delivery through a consistent internal UI component library.

Experience

Work history, roles, and key accomplishments

Full-Stack Developer

Selenium - US Startup

Jan 2025 - Dec 2025 (11 months)

Re-architected and launched an offline-first PWA, enabling field inspectors to operate seamlessly without internet connection. Owned end-to-end production deployment (monitoring and rapid recovery), partnered with Product to redesign critical UX flows, and fixed legacy bugs and data ingestion issues.

React Next.js TypeScript Go GraphQL Kafka AWS PostgreSQL PWA Redis

Full-Stack Developer

Light-it

Apr 2024 - Jan 2025 (9 months)

Developed a lead-management admin portal from scratch using React and Node/Fastify. Led architectural refactoring, drafted Stripe integration architecture for subscriptions and add-ons, analyzed iPaaS adoption for franchise subscription models, and built internal React tutorials.

React TypeScript Fastify GraphQL Stripe Docker Radix Shadcn Ui

Full-Stack Developer

CreatorSpace - US Startup

Apr 2023 - Feb 2024 (10 months)

Re-architected an existing offline PWA to improve offline state management and UX, shipping key features to production. Owned production deployment (monitoring and rapid recovery), partnered with Product on critical UX redesigns, and resolved legacy bugs and data ingestion issues related to scraping mechanisms.

React Next.js TypeScript Go GraphQL Kafka AWS PostgreSQL PWA

Software Engineer

10Pines

Mar 2020 - Jan 2023 (2 years 10 months)

Integrated backend services with third-party systems including MERS, ACES, and Byte, and co-built an internal UI component library using Chakra UI to accelerate delivery across multiple squads. Acted as a Scrum Master (certified in 2022), maintained unit/integration test coverage, and drove hackathons through rapid prototyping and cross-team collaboration.

React Next.js GraphQL Kotlin Spring PostgreSQL Stripe Chakra UI Datadog

Freelance Developer

Freelancer

Jun 2019 - Feb 2020 (8 months)

Delivered web and mobile development work for clients including Filtomat Water Systems, Ticmas, and Alibrate. Built features using React Native, React, Redux, AngularJS, Node, and PHP/Laravel with REST and supporting analytics and database integrations.

React Native React Redux AngularJS PHP Laravel MySQL Docker REST

Full-Stack Developer

GeoPagos

Jun 2018 - Apr 2019 (10 months)

Implemented features across client dashboards and a bank’s dashboards for a Latin American digital payments platform. Worked across backend and frontend using Symfony-based PHP services, REST, Docker, and JavaScript/TypeScript tooling.

Symfony REST APIs Docker React TypeScript Express Koa

Consultant

Lagash

Jan 2017 - May 2018 (1 year 4 months)

Served as a consultant delivering a content management system for clarovideo.com (AMCO) and improving the publisher platform based on user feedback. Contributed to search and recommendation capabilities by implementing APIs using ElasticSearch/Kibana/PredictionIO and monitoring with New Relic.

JavaScript Elasticsearch Kibana New Relic MongoDB PredictionIO

Consultant

Truelogic

Feb 2014 - Nov 2016 (2 years 9 months)

Delivered CRM and CMS implementations and ongoing maintenance for US clients. Supported business systems through configuration, maintenance, and delivery of incremental fixes and updates.

CRM Implementation CMS Implementation Maintenance client support Web Applications

Software Developer

Zedplan

Feb 2011 - Dec 2013 (2 years 10 months)

Developed software for SMEs using PHP MVC frameworks such as Symfony 2. Built and maintained web applications to support business operations and customer needs.

PHP Symfony MVC Web Application Development SME