Based in Barcelona · open to relocating

Bart Zanen

Full-Stack Software Engineer

I build full-stack web apps with AI in the stack — from fine-tuned on-device models to the interface around them. Currently co-founding Journii, and open to full-time roles.

See my work Download CV

About

I'm a software engineer who likes building things end to end, from the database up to the interface someone actually clicks on. My happy place is full-stack web development, especially when AI is part of the stack. I've spent the last couple of years getting hands-on experience building AI-adjacent tooling, which I think is becoming essential in this field.

While studying Computer Science at UPC in Barcelona, I spent six months on exchange in Bergen, Norway. After it ended, I chose to stay a while longer, finishing my thesis remotely and working as a Head Waiter leading a team at a high-volume restaurant to support myself in the meantime.

Once I wrapped up my degree, I took a few months to backpack through Southeast Asia, meeting people building all kinds of remote and independent careers along the way. I came back wanting to keep learning and building — which is what I'm doing now, co-founding Journii and shipping side projects like Dici to stay close to the parts of this field that are moving fastest.

Full-stack development
Trained & deployed ML models
Led teams under pressure
AI-adjacent tooling
5 languages spoken
Fast learner, fast mover

Experience

Engineering

Jun 2026 — Present · Remote

Co-Founder · Journii

Architected and developed core software for two applications (Next.js web, Expo mobile), establishing monorepo structure, CI/CD, and Cloudflare deployment.
Built an internal GitHub package system centralizing UI components, types, and themes for reuse across all applications.

Apr 2024 — Jan 2025 · Sabadell, ES

Software Engineer Intern · Rosepetal

Increased dataset labeling efficiency by 35%, as measured by the labeling team, by building a solo Python integration of Meta's Segment Anything Model into the internal labeling editor.
Selected Segment Anything Model over two competing models after independent research and testing; the integration is still used company-wide across all datasets more than a year later.
Designed and built the card components and routing for a client dashboard used by 15+ clients managing 120+ datasets, owning the Figma design within a three-person team over four months.
Developed and improved software for AI-driven quality control systems, supporting automated defect detection and process monitoring on industrial production lines.
Identified and resolved performance bottlenecks across the application, improving responsiveness and overall system stability.

Other experience

Apr 2025 — Jan 2026 · Bergen, NO

Head Waiter · Villa Paradiso

Led and coordinated a waitstaff team in a high-volume restaurant serving 150+ guests simultaneously.
Managed reservations, guest requests, and table coordination, keeping service running smoothly under nightly pressure.
Trained and onboarded new staff on service procedures, helping maintain consistent standards across the team.
Collaborated cross-functionally with kitchen and bar teams to streamline communication and improve guest experience.

May 2024 — Sep 2024 · Barcelona, ES

Tour Guide · Self-Employed

Built and ran an end-to-end bike tour business, handling bookings, payments, scheduling, and customer communication.
Led tours for groups of up to 10, adapting routes and storytelling to different group sizes and interests.
Maintained a 5-star customer rating across the season by tailoring each tour to guest interests.

Feb 2023 — Feb 2024 · Barcelona, ES

Team Coordinator · FieldHockeyTravel.com

Coordinated transportation and logistics for international hockey teams, including airport transfers and bus schedules.
Acted as the main point of contact between drivers, venues, and event organizers to prevent delays during tournaments.
Provided on-the-ground assistance and recommendations to visiting teams throughout their stay.

Projects

Dici

A privacy-first Italian tutor that runs entirely on your device. I fine-tuned a Qwen 3.5 4B model with LoRA on a custom dataset of 1,000+ tutor-student exchanges to match a target teaching tone, then served it locally with MLX. It gives real-time conversation feedback, turns mistakes into spaced-repetition flashcards, and keeps you moving with daily AI challenges. Everything stays local—no cloud, no accounts. Built with Next.js.

Next.js
TypeScript
IndexedDB
MLX
LLM Fine-tuning
Prompt Engineering
Qwen

Live ML Model Frontend

AiGile 2.0

My Bachelor's thesis at UPC (graded 8.3/10) — the second iteration of AiGILE, an AI-powered platform for teaching agile methodologies in a university Software Project Management course. Developed solo over one semester: AI-orchestrated simulations that adapt to student-submitted startup ideas across four scenario types, plus a custom scenario builder for instructors.

Django
OpenAI API
PostgreSQL
Docker
Education

Code · Private

Pulmón Urbano

A mobile app for athletes in Barcelona, combining a real-time air quality map with route planning that favors cleaner-air paths, plus social features like activity tracking, a community feed, friends, and chat. I led the 4-person team and owned the software architecture and the OSRM routing integration, wired to Barcelona's open air-quality API. Built with React Native/Expo and a Django backend.