About
I am Hernán De Souza, also known as Erno. I live in Buenos Aires, Argentina (UTC-3) and work in English and Spanish. I have built software professionally since 2010.
Today I am an AI Engineer at MODO, a fintech in Argentina, where I take LLM applications from prompt design to production APIs. Before that I worked as a senior frontend developer and as a full-stack developer on fintech, education, media and e-commerce products.
I am looking for Forward Deployed Engineer roles. Outside work I build my own product, Firulapp, and open-source tools for agent workflows.
Experience
AI Engineer · MODO
Jan 2026 – present
LLM applications from prompt design to production APIs. Generative Engine Optimization for AI search surfaces, tracked with mention rate, citation share and traffic attribution. OpenAI, Anthropic and Gemini APIs integrated into product surfaces. Internal AI tools that automate repetitive processes. Legacy stack modernization with AI-assisted tooling.
Senior Frontend Developer · MODO
Apr 2024 – Dec 2025
Led a multi-brand Next.js (SSR) module with a themeable Tailwind design system and per-client configuration. Unit and integration tests, release monitoring and A/B tests. Agent automations for postmortem review and an MCP server connecting product data to ChatGPT. Shared component library, RFCs, demos and technical proposals.
Full-stack Developer · Freelance
Jan 2023 – present
Direct client work: an e-commerce platform for automotive products (Strapi, Next.js, Postgres, MongoDB, Redis), a long-standing media client, FWTv (Angular, Node, Express, MongoDB, Redis, AWS S3), and a football player pass management app (Next.js, Redis). Auth with Passport.js, tests with Jest and Cypress.
Senior Full Stack Developer · True North
Oct 2020 – Jan 2023
Two fintech projects on Node, Express, MongoDB and React: loan application flows, third-party integrations (credit scoring, real-time financial data verification), digital document signature and stakeholder dashboards tracking each application.
Senior Web Application Developer · VIDA Tec
May 2019 – Oct 2020
Education platform on Angular and NgRx, NestJS, AWS Lambda and S3, and MongoDB, with guided product tours.
Full Stack Developer, UI Lead · Belatrix Software
May 2016 – Feb 2019
UI architecture for an analytics and data-mining tool with most processing on the client. UI lead on an Angular and Redux project. Gave internal talks on Angular Elements, Aurelia and NgRx.
MEAN Stack Developer · FansWorld TV
Sep 2013 – Mar 2016
API, admin panel, Angular frontend, PhoneGap mobile app, push notifications and video processing for a social video platform.
Front-End Developer · MRM Worldwide
Jul 2012 – Sep 2013
Production front-end for agency clients across LAMP, .NET and Java stacks, with distributed teams.
Front-End Developer · 8A Marketing
Jan 2010 – Jul 2012
Microsites, newsletters and CMS pages.
How I work
Think before coding
State assumptions, name the confusion, propose the simplest option. Ambiguity gets a question, not a guess.
Simplicity first
The minimum code that solves the problem asked. Nothing speculative. If a senior engineer would call it overcomplicated, it is.
Honest reporting
I report results as they are. If a test fails, I say so. I write down what worked and what broke.
Spec before code
For new features and architecture decisions I write the spec first, in Given/When/Then form. The judgment is the work.