01 / What I bring
The front end.
Fast, accessible interfaces, with the detail work that makes them easy to use.
Esteban Leandro Marin
Full-stack software engineer
Built with purpose.
Big ideas. Built right.
I'm Esteban, a software engineer at Xbox, working on new ways for people to play.
Full-stack engineering and applied AI, built around the people using them.
01 / The person behind the pixels
Serious
craft.
Playful mind.
10+ years of building useful digital products.
I've worked with small businesses, large outsourcing companies, remote teams, and big tech. Different environments have shaped how I collaborate, solve problems, and build software.
I'm a full-stack developer who cares about performance, usability, and accessibility. I enjoy turning ideas into products that feel good to use and make a real difference.
02 / What I bring
Across the stack.
Connecting interfaces, services, and data. Learning the systems a problem needs.
03 / What I bring
Applied AI.
Harness engineering that connects models to context, tools, and workflows, with evaluation tied to a clear goal.
04 / What I bring
Cloud & data.
My latest work includes Azure and Databricks, with Bicep and Terraform for infrastructure as code.
02 / Experience
More people.
More play.
At Xbox, I'm working on new ways for players to play more, more affordably.
December 2024 - present
Microsoft / Xbox
Software Engineer
Xbox Experiences and Platforms
I work across Xbox on web, Android and iOS, console, PC, smart TVs, and handhelds. Getting a new experience working across that ecosystem means understanding how each client is built and how it connects to the rest of the platform.
Some of the hardest problems involve several parts of the stack at once. I work through those with the team, from React and React Native interfaces down to C++/C# client code and backend services. On the Xbox and PC clients, that includes React Native for Windows and C++.
The goal is to bring video games to more people. I'm helping build more affordable ways to play, so players have more options for how and where they can get into a game.
Earlier experience
Zonda July - December 2024
Full-stack developer, continuing my work after Zonda acquired Outcoding.
Outcoding 2016 - 2024
Eight years growing from JavaScript customization through performance-focused development to full-stack engineering.
03 / Applied AI
A goal first.
Then the tech.
At Xbox, I'm helping shape how we apply AI to real engineering problems.
I start with what we want to make possible for players or the team, not with a model we want to try. That means defining what should improve, choosing an approach that fits, and evaluating it against that goal.
I'm curious about what's new, but deliberate about where it belongs. The point is to give people more room to think, create, and solve problems, not add AI for its own sake.
Harness engineering.
I build AI harnesses: the systems around a model that manage context, connect tools, carry state through a workflow, and handle failures. That includes retrieval-augmented generation (RAG), embedding databases, and shared team knowledge, so the model can work with relevant information rather than an isolated prompt.
Evaluate the result, not the novelty.
I build evaluation harnesses to compare behavior, understand failure cases, and assess whether a change moves us closer to the intended outcome. A convincing demo is a starting point, not evidence that a system is ready to rely on.
My broader hands-on work includes AI-powered platforms, WhatsApp chatbots, and shared second brains for teams. Those experiences inform how I approach new possibilities: start with a need, build, and find out whether it actually helps.