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Hi, I'm Tomás ✦

I build productsthat work.

Frontend DeveloperJavaScriptReactNext.jsReact Native

5+ years building web and mobile apps for companies in Spain and Argentina, from the first design to production.

Open to work · Remote or hybrid

Get in touchDownload resumeView in VS Code mode

Buenos Aires, Argentina

JS tomas.js
1const tomas = {
2  role: "Frontend Developer",
3  stack: ["React", "Next.js", "React Native"],
4  experience: "5+ years",
5  basedIn: "Buenos Aires",
6  openToWork: true,
7};
8
⎇ main · availableOpen in VS Code mode

01 — About me

Code with judgment.

From the first design to production, focused on user experience and on products that actually work.

I'm a Frontend Developer with 5+ years of experience building web and mobile apps with JavaScript, React, Next.js, and React Native for companies in Spain and Argentina, from the first design to production.

Since 2026 I've also been Systems Manager at ST Group, leading infrastructure, cybersecurity, and custom software for 5 corporate clients. This gives me an end-to-end view of product, business, and infrastructure.

  • Clean, maintainable code
  • Strong focus on UX
  • Ownership from idea to deployment
  • Clear communication
Tomás Vallejos Semino
Open to work

Tomás Vallejos Semino

Frontend Developer

Buenos Aires, Argentina

5+

years of experience

Web & Mobile

products in production

0 → 1

from design to production

ES · AR

companies in Spain and Argentina

Education

  • B.S. in Cybersecurity — UNSO

    In progress · 2nd year

  • Full-Stack Program — Plataforma 5

    2021

  • Fortinet Certified Fundamentals in Cybersecurity

    2026

Languages

  • Spanish

    Native

  • English

    Upper-intermediate · B2

02 — Projects

Things I made real.

Products and platforms that solved concrete problems.

01Internal use

Flechabus

Bus driver app

Production mobile app for the drivers of a group of long-distance bus companies: ticket and ID scanning, stop tracking and offline support. MVP in 3 months.

  • React Native
  • Expo
  • Figma
02Live demo

Personal project

VS Code–style portfolio

My portfolio as an interactive code editor: files, tabs, a terminal, git history and skills as extensions.

  • Next.js
  • React
  • Tailwind CSS
Live demoCode
03Production

Hetmo

Production metrics

Real-time dashboards of daily and monthly production for window factories, with efficiency checks.

  • React
  • Next.js
  • Vercel
04Automation

ST Group

Jira integrations

Automation and per-area metrics for a corporate client, plus custom apps connected to the Jira API.

  • React Native
  • Next.js
  • Jira API
05B2B

Laboratorio Córdoba

Medical tests portal

Platform for companies to manage their employees' medical tests, integrated with a lab.

  • React
  • JavaScript
06Real time

Vidual

Service marketplace

Platform to publish and hire services, with reviews and real-time chat between users.

  • React
  • Next.js
  • Socket.io

03 — Experience

Experience that adds up.

From my first role to today. Each one has its full file in VS Code mode.

  1. Jan 2026 – Present

    Buenos Aires

    Systems ManagerCurrent

    ST Group

    Systems area for 5 corporate clients: infrastructure, security, leading the helpdesk team and custom software.

    React NativeNext.jsPWAJiraSee details →

  2. Sep 2024 – Present

    Freelance

    Frontend & Mobile DeveloperCurrent

    Flechabus

    Mobile app for bus drivers, from the Figma design to production, built to work even without signal.

    React NativeExpoJavaScriptFigmaSee details →

  3. Jul 2023 – Present

    Freelance

    Frontend DeveloperCurrent

    Buspack · Flechabus group

    Parcel and logistics platform: new features, mobile design and a web app integrated with a locations API.

    ReactNext.jsNode.jsDockerSee details →

  4. Aug 2023 – Sep 2026

    Full-time · Remote, Spain (Cantabria)

    Frontend Developer

    Hetmo Informática

    Window and door quoting software with clients across Europe and Latin America; led the first mobile version.

    JavaScriptReactNext.jsVercelSee details →

  5. Apr 2023 – Aug 2023

    Freelance · Remote

    Frontend Developer

    Vidual

    Service marketplace with reviews and real-time chat.

    ReactNext.jsSocket.ioNode.jsSee details →

  6. May 2022 – Apr 2023

    Freelance · Remote

    Frontend Developer

    Laboratorio Córdoba

    Platform for companies to manage their employees' medical tests.

    ReactJavaScriptSee details →

  7. Aug 2021 – Apr 2022

    Full-time · Remote, Argentina

    Frontend Developer

    NetGlobal Solutions

    My first role: a CRM and a PWA for DirecTV with geolocation, plus tests with Jest and RTL.

    ReactPWAJestReact Testing LibrarySee details →

04 — Challenges

Interesting problems.

Real constraints and how I solved them.

01

Working without internet

Flechabus

Buses travel through areas with no signal. The app validates passengers offline and syncs when the connection comes back, without losing any data.

02

Modernizing legacy code

Buspack · NetGlobal

Migrating class components to modern React with hooks and updating dependencies, without breaking production.

03

Real-time chat

Vidual

Instant messaging between users with Socket.io, the project's biggest technical challenge.

04

Automating a company

ST Group

Jira rollout across several areas of +Vida, with metrics and custom apps built on its API.

05 — Skills

My toolbox.

Frontend

  • JavaScript×3
  • TypeScript
  • HTML5
  • CSS3
  • Sass
  • React×5
  • Next.js×4
  • Redux
  • Tailwind CSS
  • Material UI
  • CSS Modules

Mobile

  • React Native×2
  • Expo×1
  • Expo EAS

Backend

  • Node.js×2
  • Express
  • NestJS
  • REST APIs
  • Socket.io×1

Databases

  • Supabase
  • Firebase
  • PostgreSQL
  • MySQL
  • MongoDB

Testing

  • Jest×1
  • React Testing Library×1

06 — Tools

What I use every day.

  • 01Git
  • 02GitHub
  • 03Docker
  • 04Vercel
  • 05AWS
  • 06Heroku
  • 07Railway
  • 08Figma
  • 09v0
  • 10Jira
  • 11Notion
  • 12Scrum
  • 13Claude Code
  • 14Cursor
  • 15ChatGPT

VS Code mode

Want to see this portfolio as a real project?

VS Code is the code editor millions of developers use every day. I built a second version of this portfolio that works like that editor, with all the same content.

No coding knowledge needed: it's designed to be explored with clicks.

  • Folders and filesEvery role, project and certificate is a file that opens in tabs.
  • A real terminalType help and try commands like whoami, experience or coffee.
  • My career as git historyEach role is a commit, from the latest to the first.
  • Skills as extensionsMy technologies show up as installed extensions.
Open VS Code mode

Best on a computer. To come back, use the Home button.

07 — Beyond code

I also like to slow down.

Certified barista — Barista & Latte Art Course · Puro Lab, Escuela de Baristas (2026).

If we hop on a call, the coffee's on me.

Certified baristaView certificate →

08 — Contact

Shall we talk?

If you have a project, an opportunity or just want to exchange ideas, write to me.

tvallejossemino@gmail.com
Send email LinkedInGitHub
Descargar CV (ES) Download Resume (EN)