Software Engineer · AI Builder · South Florida
Ideas in.Products out.
I'm Nathanael Castro. I build AI products end to end, from schema to model to interface, and I ship them. The skyline behind this is generated and rendered live in your browser, because a portfolio should prove something, not just claim it.
Projects.
Featured / React Native / iOS & Android
Truth Talks
Kids hold real conversations with AI biblical characters. The hard part was never the chat; it was building safety a parent would actually trust: layered moderation, parental controls, and COPPA compliance baked into the architecture instead of bolted on.
Read the case study
Hackathon / Full-stack
NutriFit
An AI meal-and-workout planner built, demoed and finished inside the hackathon clock: dashboards, weekly planners, and rate-limited AI that adapts to the person instead of handing them a static PDF.
Read the case study
TypeScript / LLM product
Frank
A budgeting assistant with an actual personality. Frank is blunt on purpose. Most finance tools are passive spreadsheets, and nobody ever changed a habit because a pie chart looked concerned.
Read the case study
Open source / Agents
llm‑in‑chrome
A browser agent that reads pages, decides, and acts, behind an interface that doesn't care which model you plug in. Most agents are welded to one vendor. This one isn't, and that was the whole point.
Read the case study
AI planning / Routing
El Camino
A trip planner that designs the whole journey (route, stops, and pacing) around how you actually like to travel, instead of dumping the top ten attractions and calling it an itinerary.
Read the case study
AI is a material, not a magic trick. It still has to be engineered.
01
Find the real constraint
Every project has one thing that decides whether it's viable. For a kids' AI app it was safety, not the model. I go looking for that first, because everything else is negotiable and it isn't.
02
Design the data before the demo
Schemas outlive prompts. I redesigned a production MongoDB layer at OneHope before touching features, because a fast demo on a bad schema is a slow product six months later.
03
Put it in front of people
I ran A/B tests and focus groups with 35 participants rather than guessing. Opinions are cheap; watching someone get confused by your UI is worth a week of debate.
04
Ship it, then watch it
Deployed isn't done. Rate limits, CloudWatch alarms, moderation logs: the boring layer is what separates a demo from something you can leave running.
Both halves are true, and that's the whole point.
I'm a CS senior at Florida Atlantic University, minoring in Artificial Intelligence & Cybersecurity, graduating May 2026. Last summer I was the sole engineering intern at OneHope, with no team to hide behind, and I shipped an AI assistant into production, redesigned the database under it, and ran the research that decided what got built.
Away from work I keep building: an app where kids talk with AI biblical characters, a budgeting assistant too blunt to be polite, an open-source browser agent. The pattern is always the same: I get curious about something, then I get stubborn about finishing it.
- Based
- South Florida. Open to remote & relocation
- Looking for
- New-grad software / AI engineering, May 2026
- Currently
- Building agent tooling and shipping Truth Talks
- Off-hours
- Hackathons, WebGL rabbit holes, and this website
A small scripted assistant.
Track record.
Jun to Aug 2025 · Pompano Beach, FL
AI Software Engineering Intern
OneHope
- Sole intern engineer. Built and deployed an AI chatbot (OpenAI API, Node.js, MongoDB) that lets employees retrieve info, answer event questions, and auto-generate meeting summaries.
- Architected a full MongoDB redesign for a production system monitored with AWS CloudWatch, improving query performance and scalability.
- Drove feature decisions through A/B testing and focus groups with 35 participants; built the backend survey flows and shipped the frontend conversation-starter UI.
Graduating May 2026
B.S. Computer Science
Florida Atlantic University · minor in AI & Cybersecurity
- Data structures & algorithms, database systems, software engineering, full-stack and iOS development, artificial intelligence.
Certifications
Google AI Essentials
HackerRank Python · Microsoft Foundational C# (in progress)
Languages
AI & ML
Frameworks
Data
Cloud & practices