Open to opportunities

John Jairo Castillo Cortes

@johnjairocastillocor

Frontend Developer crafting React/Next.js products and agentic AI workflows to deliver fast, high-impact user experiences.

Colombia

Message

What I'm looking for

I want to build high-performance frontend products with React/Next.js while integrating agentic GenAI workflows. I’m looking for a team that values scalable architecture, measurable outcomes, and shipping fast with solid testing and collaboration.

I’m a results-driven Frontend Developer and AI solutions builder with over 7 years constructing high-performance digital products. I focus on the intersection of modern Frontend architectures—React, TypeScript, and Next.js—and AI-driven systems design that solves real business logic.

I specialize in orchestrating AI agents and multi-LLM workflows, using advanced prompt engineering to build autonomous workflows. I’ve integrated Generative AI tools and LLM orchestration workﬂows to streamline software development timelines and deliver next-generation digital products.

I’m pragmatic about outcomes: I’ve architected and deployed React/Next.js applications that boosted user retention by almost 30%. I’ve also led platform UI/UX overhauls, established scalable design systems, and ran continuous usability testing—improving customer satisfaction by 40% and task completion rates by 25%.

I’m equally strong on engineering fundamentals and collaboration—building reusable component libraries, implementing robust testing with Jest and React Testing Library/Enzyme, and partnering with design teams for pixel-perfect Figma-to-code execution. I work across state/data management (Apollo GraphQL, Context API, Zustand, SWR, TanStack Query) and performance-focused frontend design to help teams ship faster with less technical debt.

Experience

Work history, roles, and key accomplishments

Current

Front End Developer

Current

Monkey in Motion

Sep 2024 - Present (1 year 9 months)

Built high-performance web applications with React and Next.js, boosting user retention by almost 30%. Integrated generative AI and LLM orchestration to streamline development timelines and delivered a UI/UX overhaul that increased satisfaction by 40% and task completion by 25%.

React Next.js TypeScript Orchestration Prompt Engineering Generative AI UI UX Design Systems Material UI

Front End Developer

8Base

Jan 2023 - Sep 2024 (1 year 8 months)

Designed and engineered dynamic cloud-native UI with React and Material UI, increasing user engagement by 25%. Implemented Apollo GraphQL client data management, reducing page load latency by 40%, and applied advanced prompt engineering to accelerate AI feature adoption.

React Material UI Apollo GraphQL State Management TypeScript Performance Optimization SWR Prompt Engineering Jest

Front End Developer

TanStack Gorilla Logic

Jan 2020 - Apr 2023 (3 years 3 months)

Developed reusable React component libraries to accelerate product deployment cycles for internal teams. Improved quality by implementing unit and integration testing with Jest/Enzyme and optimized client performance using Redux state management with SWR caching.

React Redux SWR Tanstack Query Jest Enzyme Component Libraries Figma Unit Testing Integration Testing

Front End Developer

NTT Data

Jan 2019 - Apr 2020 (1 year 3 months)

Built enterprise web applications using Angular and React for major corporate clients. Optimized SASS/CSS styling pipelines for cross-browser compatibility and delivered Agile/Scrum projects consistently 15% ahead of projected schedules.

Angular React JavaScript SASS CSS3 Browser compatibility Agile Scrum Accessibility Standards Git

Front End Developer

Globant

Jan 2017 - Nov 2019 (2 years 10 months)

Architected scalable frontend structures using BEM methodology and SASS, improving maintainability and reducing style conflicts. Wrote optimized JavaScript (ES6+), HTML5, and CSS3 while following accessibility and best-practice standards.

BEM SASS Javascript (ES6)HTML5 CSS3 Frontend Architecture Accessibility Responsive UI Git Github Testing

Front End Developer

IFX Networks

Jan 2015 - Oct 2017 (2 years 9 months)

Translated complex B2B technological frameworks into user-centric interfaces, improving digital adoption by 25%. Developed data-driven UI/UX-aligned content and product strategies that supported a 10% growth in lead generation.

UI UX Design JavaScript Responsive Design CSS3 HTML5