Product engineering
End-to-end delivery of desktop, web and mobile products — architecture, data management, and visual interfaces.
- Web & desktop apps
- Cross-platform mobile
- APIs and data layers
XF Design · Independent studio
Engineering systems. Designing interactions.
Interactive Systems Engineer
I design and build software where computation, data and interface meet — web products, real-time 3D environments and the systems underneath them. From the first sketch to the deployed release.
+15 years Building software
PhD · PMP Certified Systems engineering
From IoT to the Cloud Rust · Python · React TypeScript
What I build for clients
Real-time, distributed, and 3D
Interactive environments that stream real geographic and engineering data, built to work on the devices people actually own.
- WebGL / WebGPU scenes
- Data streaming (e.g. geospatial)
- Financial data streamed to thousands of clients
- Physics and simulation
Interaction & systems design
UI/UX research: prototypes and interface systems that make a complex tool feel obvious. The part between the system and the person.
- Prototypes
- Design systems
- Technical discovery
Selected work
Two projects, two problems
01 Digital product
Forretas nas Contas
Split expenses. Keep good company.
Splitting costs with friends shouldn’t mean handing a company a map of your life.
Every shared expense says who you live with, where you went and what you spent. Most bill splitters keep all of it readable on their servers. This one gives a group a shared, exact ledger nobody but the group can read — including me.
Read the case study
Live product 02 Interactive 3D systems
XF Design
3D Ocean & Earth Explorer
Explore the real seabed from a browser tab.
Maritime work is explained with maps built for specialists, on machines and licences most of the room does not have.
Land, coast and seabed in one continuous Three.js scene, streamed from published data and flown through in the browser. Measured bathymetry and real infrastructure coordinates — with every layer declaring whether it is measured or illustrative.
Read the case study
In development Expertise
I work across the whole stack of an interactive product — the parts that compute, the parts that render, and the parts people touch. That overlap is where digital twins, data-heavy tools and products like Forretas get built without a translation layer losing the intent between design and engineering.
Systems & backend Rust · TypeScript · Python
Front-end & mobile Astro · React · React Native
3D & game engines Three.js · WebGL · WebGPU
Geospatial & data Tiles · bathymetry · streaming
Performance Rust parallel compute · profiling
Delivery PMP · technical leadership
About
XF Design
Engineering, interactivity and usability belong together.
I'm Xavier Fonseca, an interactive systems engineer. I do research and development for over 15 years: a PhD in location-based serious games, high-performance and distributed computing work, and years leading engineering projects on IoT, digital transformation, simulation and product work.
XF Design is where that comes together as an independent practice: I take on the projects where something complex has to become something people can actually use.
Credentials
A verifiable track record.
Research profiles, active professional certifications, degrees and awards — all linked to the issuing body.
Reach out
Have a system that needs to become an experience?
Product builds, 3D and visualisation work, architecture reviews, overall systems engineering, or a second pair of hands on something already in flight. Tell me what you're making.