Cosme Valera Reales

Software Engineer

About

Over four years building web applications. Right now I work at GMV on Galileo, Europe's satellite navigation system, across the whole stack: React and TypeScript interfaces, the Node and Java (Spring) services behind them, and the Kubernetes releases that ship them.

AI is part of how I work every day. I've built projects with Claude Code, Codex and Cursor, and I go well past the chat box into agents, skills, rules and MCP servers. I follow the space closely and keep whatever survives contact with a real project, which is also how RabbitHole got built.

That raised the bar for the basics instead of lowering it. A lot of what I ship now starts as agent output, so reviews, tests and refactoring are what keep it honest, and a clear codebase is the one an agent gets right on the first try. The standard does not change because the author is not human.

“I consider Cosme to be a serious professional, focused on continuous learning while also encouraging a positive work environment.”

— Cristóbal Seco Fiastre, Tech Lead at Capgemini

Experience

Mid-Level Full Stack Engineer

GMV Madrid, Spain

10/2023 – Present3 yrs 1 mo

Contributed to the development and delivery of web applications to meet ESA's needs in the Galileo project. Galileo is Europe's global satellite navigation system.

Developed and maintained 5+ web applications using React, TypeScript, Node and Java (Spring), improving usability and consistency across Galileo applications.
Designed and built from scratch, with my team, the backend of a web application in a Turborepo monorepo: Node, TypeScript, Express and Sequelize, with the data models and the REST endpoints its frontend consumes.
Volunteered to lead the team's move to Kubernetes: learned Kubernetes, Kustomize and Helm, then moved our Dockerized apps to Helm releases across 2 environments, reducing manual steps.
Automated monthly deployments of applications across environments using Jenkins.
Worked with ESA engineers in a Scrum team to clarify requirements, gather feedback and turn operational needs into user stories and features.
Improved maintainability through code reviews, pair programming, refactoring and clean code principles.

React
TypeScript
CSS
Node
Express
Sequelize
Java (Spring)
PostgreSQL
Docker
Kubernetes
Helm
AWS
Jenkins
Claude Code
Git
Scrum

Junior Full Stack Engineer

Seanchas Research Cork, Ireland

04/2023 – 07/20234 mos

Very enriching Erasmus+ experience working full-time in English in Ireland.

Developed and updated 2 web applications: one full stack application using Angular, TypeScript, CSS, Java and MySQL, and one WordPress-based website.
Used Git and GitHub Actions to support version control and deployment workflows.

Angular
TypeScript
CSS
Java
MySQL
WordPress
Git
GitHub Actions

Junior Full Stack Engineer

Capgemini Murcia, Spain

04/2022 – 04/20231 yr 1 mo

Developed web applications for ADIF railway infrastructure systems, supporting services related to Renfe trains and national rail operations, using Angular, TypeScript, CSS and Java (Spring).
Built responsive interfaces from Figma designs and client requirements, aligning frontend implementation with business and usability needs.
Started with Angular and Java. Three months as an intern, then hired.

Angular
TypeScript
CSS
Java (Spring)
PostgreSQL
Git
Figma
Scrum

Projects

RabbitHole Flagship project

Learn anything through what you already know.

Source Visit site How I built it

2024 – 2026

Designed, built and run by me over 6+ months of focused work spread across two years. One prompt becomes a multi-page guide with lessons and exercises, explained through the background knowledge the reader picks, and it keeps growing on demand through an AI chat with web sources. Any guide turns into a quiz, flashcards or a two-voice podcast in one click, and it all runs on the AI you choose: hosted, your own API key, or a local model on your machine.

React
TypeScript
Turborepo
Serverless
Supabase
Stripe
Vitest
Playwright

DevOps Lab

One full stack app, deployed with Docker, Kubernetes and a Jenkins pipeline on AWS.

Source Visit site

A hands-on lab that takes the same full stack application through every common way of shipping it: Docker Compose, Kubernetes with Kustomize and Helm, and a Jenkins CI/CD pipeline, each with its own tutorial. The live version runs on AWS (S3 and CloudFront for the frontend, Lambda for the API, Jenkins on EC2) and shows the real status of its Jenkins pipeline.

React
TypeScript
Node
Express
Docker
Kubernetes
Helm
Kustomize
Jenkins
AWS

Sympho

Compose, save and play sheet music, on the web or as a desktop app.

Source Visit site

A score editor that runs in the browser or as a desktop app: write notes and rests of any duration, add accidentals and dots, set the title, instrument and tempo, then play the score back. Sign in with Google to save scores to a private repository, or publish them to a public one that everyone can browse.

JavaScript
Node
VexFlow
Electron
Kubernetes

Bitcoin Finance Lab

Bitcoin against the stocks and indices that hold it, charted.

Source Visit site

A finance tool that puts Bitcoin side by side with Bitcoin treasury companies such as Strategy and Metaplanet, Strategy's preferred shares, broad indices like SPY and QQQ, or any ticker you add. The portfolio builder blends weights into returns, volatility and maximum drawdown, the benchmark view normalises returns into a sortable metrics table, and a DCA simulator shows what buying on a schedule would have done.

Vue 3
TypeScript
Pinia
Chart.js
Vite
Yahoo Finance

Skills

Frontend

React
TypeScript
JavaScript
Angular
Vue
SCSS / CSS
HTML

Backend and data

Node
Java (Spring)
PostgreSQL
MySQL
MongoDB
REST APIs
GraphQL

DevOps and cloud

Docker
Kubernetes
Helm
Kustomize
Jenkins
GitHub Actions
AWS

AI tooling

Claude Code
Codex
Cursor
Agents
Skills
Rules
MCP servers
Prompt design

Ways of working

Clean Code
Code Reviews
Pair Programming
Testing
Scrum
Agile

Education

Technician in Development of Web Applications

CIFP Carlos III

2022 – 2023

JavaScript
PHP
Laravel
MySQL
Angular

Technician in Development of Cross-platform Applications

IES Ginés Pérez Chirinos

2020 – 2022

Java
Android
Python
Oracle SQL
MongoDB
Firebase

Languages

Spanish Native
English C1 (Cambridge)
French B1