Júlio César Oliveira Rios — Full-Stack Software Engineer

Full-stack software engineer who starts from the business problem. Proposed and led the rewrite of four legacy systems into a single ERP, and built in one week a kiosk app now running in 100+ retail stores. I lean towards the backend, and I'm drawn to game engines, embedded and distributed systems, and Rust.

Salvador, Brazil

Projects

• LyricsLens

  An open-source Linux app that shows synced lyrics on top of any window, including full-screen video. It's for people who use Linux and listen to music while they work. The protocol picked the toolkit. On Wayland a normal window can't stay above a full-screen app; only the wlr-layer-shell protocol allows it. So it's Rust with gtk4-rs and gtk4-layer-shell from the first commit. Slint was out because winit doesn't implement layer-shell, and Qt would have brought QML, CMake and a second language. The cost: GNOME doesn't support layer-shell. Players round the playback position to whole seconds, so the lyrics moved in jerks. The clock now anchors on the moment the reading ticks over (41 to 42) and runs on the machine's time from there; a big jump counts as a seek and resets the anchor.

  Rust, GTK4, wlr-layer-shell

  LyricsLens source codeLyricsLens demo

• Orbit

  A personal finance app that syncs bank accounts through Open Finance and uses AI to help people understand their money. Built end to end, from design to deploy, by one person. One repository, three shells. Web, desktop and mobile had to feel like the same app, so the apps are thin shells: shared packages hold the screens, the data hooks and the API client, and the TypeScript types are generated from the Go backend's OpenAPI spec, so a field renamed in Go breaks the TypeScript build. Web (Next.js) and desktop (Tauri) render the same components; mobile (React Native) shares the hooks and types. The paid plan lives in the database and only the Stripe webhook writes it, so a checkout redirect can never unlock it. Local mode is a product, not an offline cache: "Open locally" keeps everything in SQLite on the device, with a local router answering the same API routes and no network requests.

  Go, PostgreSQL, Next.js, Tauri, React Native, SQLite, Stripe

  Orbit demo

• how-i-build

  A template for an engineering notes site: posts and case studies written in MDX, in two languages, with a changelog read from GitHub releases.

  Next.js, Tailwind CSS, Bun, MDX

  how-i-build source codehow-i-build demo

• Diegesis

  A desktop panel for tabletop RPG game masters. It reads an Obsidian vault and shows its content in a form that's quick to use while running a session.

  TypeScript

• CHIP-8 Emulator

  A complete CHIP-8 emulator written in C with SDL2. It implements all 35 instructions and runs classic games.

  C, SDL2

  CHIP-8 Emulator source code

• Invoice Issuing API

  A REST API for customers, products and Brazilian electronic invoices (NF-e). It generates the invoice XML and calculates the ICMS and IPI taxes.

  TypeScript, REST

  Invoice Issuing API source code

Experience

• Full-Stack Software Engineer — VX Case (Oct 2025 – Present): Proposed the architecture for replacing four legacy systems (outdated Angular, NestJS microservices, C# ASP.NET, Laravel/Zend) with one Next.js + Elysia/Bun monorepo, defended it to the tech lead, and led the implementation. Cut the time to deliver a new screen from 2–3 weeks to under one day, and a heavy request from 12 s to 1.3 s after database migrations. Built a kiosk app alone in one week after meeting the CEO and marketing; plain HTML/CSS/JS with a JSON content file let non-developers update it without code. Now runs in 100+ points of sale across Brazil. Co-built the company's in-house project-management tool (Next.js + Go, magic-link auth) that replaced ClickUp for the whole company. Built most of the ERP hardware module, a Vue checkout and the Getnet payment integration. Helped design a per-project Git flow with preview environments for reviewers and PO-approved releases, reducing production/development drift. Took part in the infrastructure migration from AWS to DigitalOcean, Kubernetes and ArgoCD.
• Software Development Intern — Tecnotrends (Apr 2024 – Sep 2025): Maintained and extended a legacy C#/ASP.NET system with a React frontend and MySQL.
• IT Intern (support, DBA, networks) — SENAI CIMATEC (Jul 2022 – May 2024): Automated support and database tasks in Python; administered MySQL and Linux servers; monitored infrastructure with Zabbix.
• IT Support Intern — Bahia State Department of Agriculture (SEAGRI) (Oct 2021 – Jun 2022): Supported computers and network infrastructure, including server racks and switches.

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