Renan
Fernandes

Backend & Systems Engineer

Go · AI Architecture · Mission-Critical Systems

Curitiba, Brazil

About

Software engineer with 8+ years of experience, mostly working on business-critical enterprise systems. I started my career with COBOL and today work at Unisys on complex banking software, where changes often involve impact analysis, modernization, integrations, and systems that have been running for decades. Working in environments where reliability and traceability matter has strongly shaped how I approach software.

Most of the systems I work on professionally belong to clients and cannot be published or discussed in detail. That is why this portfolio leans toward personal projects, open-source work, and anonymized case studies rather than the majority of my day-to-day engineering work.

My current development focus is Go, along with practical applications of AI in software engineering. I am particularly interested in using AI with structured context, source evidence, reusable workflows, and human review rather than treating generated output as inherently correct.

Outside work, I am usually building something. Many of my projects start with a problem I want to solve for myself: task management, home automation, infrastructure, game tools, or simply experimenting with a technology I want to understand better. I run a Proxmox homelab, automate my home, and enjoy working across the boundary between software, infrastructure, and hardware.

I tend to learn by building and to care about the less visible parts of software: reliability, security, maintainability, documentation, and understanding how the entire system fits together.

Selected projects

Corkboard with printed tasks and QR codes

01 / TASKEMONPrinted tasks · QR codes

Watch demonstration

Personal project · Go backend

Taskemon

Go · SQLite · APIs · Security · Testing

Taskemon is a gamified task manager built around how I actually work. I have ADHD, and conventional task-management tools rarely stick for me. I wanted a tool that combines my love of gaming with the written tasks I rely on to keep track of things. The project began with an idea my brother built, which I expanded to fit my own workflow.

GitHub Web client

Project details

Expanded the original open-source project with a Go backend, Argon2id authentication, session management, CSRF protection, API keys, and rate limiting.
Added database migrations, PokéAPI integration, image processing, and ESC/POS thermal printing. Tasks become physical cards with QR codes, connecting the application to a task board I use in everyday life.
Developed documentation and automated tests alongside the implementation.

HearthPlan showing a 3D village and planning tools

02 / HEARTHPLAN3D planning

Animated demosClaim planning ↗Road planning ↗

Personal project · Planning tool

HearthPlan

TypeScript · 3D · Local-first · Testing

HearthPlan is a local-first 3D planner for villages in Haven & Hearth. It grew out of a practical problem: exploring a village layout before committing time and resources to building it in the game. It combines my interest in games with building tools that solve problems I encounter myself.

GitHub

Project details

Built an interactive 3D planning tool for exploring village layouts before constructing them in the game.
Developed the asset-processing pipeline and worked on usability, performance, and automated tests alongside the planning features.
Designed around a local-first workflow for personal planning.

Home Assistant lighting dashboard organized by room

TV and workstation controls in the living-room dashboard

03 / HOME ASSISTANTCustom dashboards

Personal infrastructure

Home Automation & Homelab

Home Assistant · Proxmox · APIs · Encrypted backups

A personal environment for home automation and self-hosted services, built around Home Assistant and a Proxmox homelab. It supports local hosting, storage, encrypted backups, and custom dashboards for everyday use, connecting software with the hardware around my home.

Case study

Integrated API-controlled computers with Home Assistant and built custom dashboards.
Built a Proxmox homelab for hosting services and managing storage and encrypted backups.
Beyond everyday convenience, I use the setup to explore integration design, infrastructure, security, and the ongoing maintenance of services I rely on.

DOCUMENTATION WORKFLOW

01
Source code
COBOL · dependencies · metadata
02
Structured knowledge
Documentation · rules · evidence
03
Human review
Confirm · correct · version

Local knowledge base · Git versioning

Internal proof of concept

Agentic AI for Legacy Systems

Go · COBOL · Structured knowledge · Human review

An anonymized case study of an internal proof of concept for using AI to support the documentation and analysis of legacy banking software. The focus is on giving AI structured, traceable context and keeping human review central to the workflow.