# Gefferson Teodoro de Souza

Backend Engineer | Node.js · TypeScript · NestJS · PostgreSQL

## Contact
- Goiânia, Brazil (UTC-3)
- geffersonteodorodesouza@gmail.com
- https://www.linkedin.com/in/gefferson-souza/
- https://github.com/Gefferson-Souza
- https://gefferson-souza-dev.vercel.app

## Summary
I am a backend engineer. I have worked as a software engineer since January 2024, and I have been on the Duofy backend since April 2025.

At Duofy I work on the backend of a multi-tenant retail platform (point of sale and ERP), with offline-first operation and Brazilian tax e-invoicing integrations.

## Experience
### Duofy, Software Engineer (APR 2025 – PRESENT)
Full-stack role, mostly backend work on a multi-tenant retail platform (point of sale and ERP), with offline-first operation and Brazilian tax e-invoicing integrations. Stack: NestJS, PostgreSQL, RabbitMQ.
- Restored sales for every affected client after a Brazilian tax authority began rejecting tax documents on New Year's Day; I diagnosed and fixed it myself, on the holiday.

### Fox Grãos, Software Engineer → Tech Lead (JAN 2024 – APR 2025)
Joined as a junior developer (Jan 2024); mid-level (Jul 2024); Tech Lead of a small team (Sep 2024).
- Automated CT-e, NF-e and MDF-e issuance: work that used to take one person full-time all year, and three at harvest, now runs when a grain-truck load ticket is created.
- Led the migration of monolithic services to Kubernetes on EKS.
- Mentored 4 developers.

## Skills
- **Languages and frameworks:** TypeScript, Node.js, NestJS, REST APIs
- **Data and messaging:** PostgreSQL, RabbitMQ
- **Practices:** Event-driven architecture, Offline-first design, Multi-tenancy, Brazilian tax e-invoicing integrations, Automated testing, Code review, Observability
- **Also used:** Rust (Axum, Tokio) (side projects), Docker, Kubernetes on AWS EKS (at Fox), Redis, MongoDB, TypeORM, Prisma, React, Electron, GitHub Actions, NX
- **Familiar:** Python, Angular, SASS, MapBox and Google Maps APIs
- **AI-assisted delivery:** Claude Code, Agent workflows, Quality gates (hooks), MCP servers

## Projects
- **Tyrus:** An experimental TypeScript-to-Rust transpiler with Axum and Tokio code generation. https://github.com/Gefferson-Souza/Tyrus
- **GoiásScript:** An esoteric programming language with a hand-written lexer and parser that compiles to JavaScript. https://github.com/Gefferson-Souza/goiasscript
- **Claude Code quality gates (hooks):** Quality gates (hooks) for AI-assisted coding, built after I analyzed 3,454 of my own sessions: 17.6% of my messages were corrections.

## About
- location: Goiânia, Brazil (UTC-3)
- time zone: UTC-3 all year, no daylight saving
- languages: Portuguese (native); English (professional written communication, conversational speaking)
- education: Technologist Degree in Systems Analysis and Development, Universidade Católica de Brasília (2024)