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Àlex Castelo MartínezÀC

Àlex Castelo Martínez

Front-end / Full-stack Developer

€300/day
Barcelona, ES
8-15 years

Average response time: A few days

Freelancer profile translated to English.
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About Àlex

Freelance Senior Software Engineer & Frontend Architect based in Barcelona 🌊 with 7 years of experience in software development and over 9 years in the digital technology sector.

My main specialty is frontend architecture — with expert focus on Vue, Nuxt, React, and Next.js — transforming business concepts and ideas into robust, fast, and scalable web pages and applications.

I have great versatility that allows me to adapt to different types of challenges as a freelancer: I can collaborate on small projects, taking an idea from a blank canvas to production, or integrate into large developments that require solving complex performance and structure problems. I bring strong product thinking and design vision, which allows me to connect technology directly with business objectives.

What truly drives me, beyond programming, is continuous learning and innovation. I keep my stack always updated with the latest technologies, including modern architecture and advanced solutions with Artificial Intelligence, to always offer the best technical solution for each project.

I am looking to collaborate remotely (remote-first) with startups, agencies, or product companies that need an independent senior profile to materialize their ideas with the highest technical quality and agility.
  • Spanish

    Native or bilingual

  • English

    Conversational

  • Catalan

    Native or bilingual

Remote only
Primarily works remotely

Experience

  • ReverseHealth
    Senior Software Engineer
    SPORTS
    May 2024 - May 2026 (2 years)
    Barcelona, Spain
    Frontend Architecture Leader specializing in infrastructure modernization, adoption of agency AIs, and optimization of agile workflows to drive technical excellence across multiple product domains.

    💡 Key Achievements and Tech Stack:

    • Architecture Migration (Monorepo & SSR): Co-led the decoupling of a legacy monolith into Nuxt 2 to a scalable Monorepo architecture. Implemented a central CMS and 3 independent applications with Next.js (SSR) under Domain-Driven Design (DDD) principles.
    • Artificial Intelligence and Agency Flows: Advanced automation of daily operations through AI. Development of skills/hooks for agents, adoption of Spec-Driven Development, and creation of custom tools with Model Context Protocol (MCP) to integrate and automate flows in Jira, Notion, Datadog, and Figma.
    • Observability and Web Performance: Implementation of monitoring and performance strategies for Node.js APIs and SSR applications, establishing key metrics with Datadog (RUM, APM, and custom monitors).
    • Design Systems: Led the company's first unified Design System. Coordinated stakeholders, designers, and developers to create a core component ecosystem integrated into the Monorepo.
    • Testing Culture and CI/CD: Eliminated deployment bottlenecks by transitioning from manual releases to an automated CI/CD pipeline, fostering a strict Automated Testing culture.
    • Agility and Mentorship: Transformed work dynamics by migrating from traditional SCRUM to highly efficient Kanban. Trained junior developers through recurring knowledge-sharing sessions.
    Next.js React.js JavaScript / TypeScript Node.js AI
  • Holaluz.com
    Frontend Developer
    ENERGY AND UTILITIES
    December 2020 - Today (5 years and 8 months)
    Barcelona, Spain
    Frontend developer in different teams working with Vue and Nuxt to develop both internal applications and the different websites of the company.
    - Maintenance and update of an in-house design system made with Vue, TypeScript, PostCSS and other technologies like Storybook.
    - Automatic testing of applications with Jest, Cypress, Testing Library, Vue test utils and other technologies.
    - Knowledge of npm and other dependency managers.
    - Automation and continuous integration with tools such as Github Actions or Jenkins.
    - Participation in back-end projects with Symfony, Spring boot, Laravel. Basic knowledge of Java, PHP, Docker, Linux or SQL.
    - Teamwork with independent teams per domain and following agile methodologies such as Scrum or Kanban.
    Vue.js Nuxt.js JavaScript / TypeScript HTML5/CSS3 Testing
  • ADman Media
    IT Project Manager
    May 2019 - December 2020 (1 year and 7 months)
    Boston, MA 02163, USA
    - Performed tasks central to program progress, including scheduling, budgeting and accounting, and resource management.
    - Projects successfully completed such as, IT team outsourcing, integration with different suppliers, migration of IT infrastructure to own data centers and several IT feature developments.
    - Sperheaded Acuity SSP integration with SSPs and DSPs (Goolge Ad Manager, Bidswitch, TheTradeDesk, Rubicon, Appnexus, among others).

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Education

  • Degree in Engineering, Telecommunications Engineering
    Universitat Pompeu Fabra - Barcelona
    2019
    Grado en Ingeniería, Ingeniería de telecomunicaciones

Skill set

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