Hi, I'm Gustavo
I design, build and ship production SaaS end-to-end.
Selected work
AI Copilot
A multi-agent AI copilot embedded across web and WhatsApp — GPT-4o, Claude and Groq with RAG, function calling and real-time streaming.
Billing Engine
A provider-agnostic payments and billing engine handling charges, subscriptions, splits and automated Brazilian tax invoices across Asaas, Stripe and Starkbank.
WhatsApp Automation
Transactional notifications, cadence engines and conversational scheduling over the WhatsApp Business API — cutting manual follow-ups by 80%+.
Multi-tenant Platform
Config-driven multi-tenant architecture with row-level security and event-driven backends, serving 100+ organizations across healthcare, finance and ISPs.
Geospatial Platform
An interactive mapping tool with Shapefile/GeoJSON import and an offline-capable React Native app for field data collection.
My stack
About
Senior Full-Stack Engineer with 5+ years shipping production SaaS platforms end-to-end — from system design and UI/UX to deployment and observability. I build multi-tenant products, provider-agnostic payment architectures, and AI-powered features that reach real users.
I've built and scaled multi-tenant products serving 100+ organizations across billing, fintech, scheduling and automation. My work spans deep AI integration (LLMs, RAG, function calling), provider-agnostic payment layers, and the cloud infrastructure underneath. I thrive in async-first, high-ownership remote environments where I can own a problem from architecture to production.
Experience
Kactuz Lab
Senior Full-Stack Engineer · Own Studio
Jan 2020 — Present
Nemu
Full-Stack Developer · Contract
Apr 2024 — Mar 2025
Begins IT Solutions
Frontend Developer · Contract
Jan 2024 — Nov 2024
Foga Games, Start Games & T.H Serviços
Full-Stack Developer
Oct 2021 — Apr 2023
Skills
- React / Next.js / Nuxt
- TypeScript / JavaScript (ES6+)
- Node.js / Fastify / NestJS
- PostgreSQL / Prisma / Supabase
- AI: LLMs, RAG, function calling
- Vercel AI SDK / OpenAI / Anthropic
- REST & WebSockets / oRPC
- AWS / Docker / Dokku / CI-CD
- Payments: Stripe, Asaas, Starkbank
- Tailwind CSS / shadcn/ui / Figma
- Testing & observability (TDD, Playwright)
Education & learning
Design Boost
UI/UX & Figma
2024 — 2025
JStack
Advanced Node.js & API Design
2023 — 2024
Rocketseat
Full-Stack Development (React, Node, React Native)
2021 — 2022
Origamid
Frontend Development & UI/UX
2020 — 2021
Languages
Portuguese
Native
English
Professional working proficiency