Projects
LiveIndependent project2026
FIT.AI
Workout app with an AI personal trainer that talks to the user, builds the week’s plan and tracks progress.
- My role
- Full stack developer. Created in Full Stack Club’s Treinos bootcamp.
- Technologies
- Next.js 16 · React 19 · Fastify · Prisma · PostgreSQL · Gemini
- Chat with the AI
- Profile lookup
- 7-day plan
- Workout logging
- Progress stats
The problem
Building a workout plan suited to your own goal and keeping up with the routine usually takes a professional or several different tools.
What I delivered
- A Gemini chat that reads and saves data by calling API functions, instead of only generating text.
- Weekly plan, timed workout sessions, and streak and consistency stats.
- Google login through Better-Auth and an API client generated with Orval from OpenAPI.
Technical decisions
Function calling instead of free text
The AI creates the plan by calling an API function, so the result becomes structured data in the database, not text to interpret.
Trade-off: the prompt and functions must evolve along with the API.
Simple layered architecture
Route, use case and database. I ruled out hexagonal architecture because this project did not need it.
Trade-off: less isolation from infrastructure if the project grows.
Outcome
Complete application live, with open source code on GitHub.