Skip to content
Gefferson Souza · Goiânia, Brazil · UTC-3

Backend
Engineer

I work on multi-tenant retail systems in TypeScript and NestJS, with offline-first operation and Brazilian tax e-invoicing integrations.

Node.js · TypeScript · NestJS · PostgreSQL · RabbitMQ

View experienceGitHub (opens in a new tab)geffersonteodorodesouza@gmail.com
  • incident

    Restored sales for every affected client on New Year's Day, after a Brazilian tax authority began rejecting tax documents. I diagnosed and fixed it myself.

  • automation

    At Fox, automated the tax-document issuance (CT-e, NF-e, MDF-e) that took one person full-time all year, and three at harvest.

  • public code

    GoiásScript, an esoteric programming language with a hand-written lexer and parser: 40 GitHub stars.

01. Experience

Most recent first. Two companies since Jan 2024.

  1. Software Engineer

    APR 2025 — PRESENT
    Duofy

    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.
    TypeScriptNestJSPostgreSQLRabbitMQOffline-firstMulti-tenant

  2. Software Engineer → Tech Lead

    JAN 2024 — APR 2025
    Fox Grãos

    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.
    KubernetesAWS EKSTax e-invoicingCT-eNF-eMDF-e
$ cd ../skills

02. Skills

The first three groups are where I am strongest. Familiar means I have worked with it, not that I run it.

Languages and frameworks

Data and messaging

Practices

Also used

Familiar

AI-assisted delivery

$ cd ../projects

03. Projects

SIDE PROJECTEXPERIMENTAL

Tyrus

An experimental TypeScript-to-Rust transpiler with Axum and Tokio code generation.

TypeScriptRustAxumTokio
View source for Tyrus (opens in a new tab)
SIDE PROJECT40 GitHub stars

GoiásScript

An esoteric programming language with a hand-written lexer and parser that compiles to JavaScript.

Hand-written lexerParserCompiles to JavaScript
View source for GoiásScript (opens in a new tab)
PERSONAL SETUP

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.

Claude CodeHooksAgent workflowsMCP servers
$ cd ../about

04. About

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.

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)
$ cd ../contact