// full-stack engineer · since 2005

LEONARDO VASCONCELLOS

From Doctors Without Borders to smart cities — two decades building the software people depend on.

I take tangled, mission-critical systems and make them scale: clean, fast, built to last.

// about · how to work with me

Hi, I'm Leonardo

Turning tangled, mission-critical systems into software people depend on.

I'm a senior full-stack engineer who's been shipping for the web since 2005 — around 70 projects across five eras of the technology. I was elected technical lead on an Ebola-response records system with Doctors Without Borders, helped scale high-concurrency SaaS at Email on Acid, and contributed to Brazil's top-ranked smart city in Itajaí. My specialty is systems where failure has real consequences: I take them — mission-critical, often tangled — and make them scale, clean and fast and built to last. I'm still hands-on every day, now AI-assisted, and I work in both English and Portuguese. Off the clock I play bass, drums, and guitar — same discipline and timing, different instrument. If you're building something that genuinely has to work, I'd like to hear about it.

// what I do

Full-stack engineering

Front to back, web and Android — React/Next, .NET, Java. The full path from database to pixel.

Mission-critical systems

Records, supply chains, public services — systems where downtime costs more than money.

Untangling legacy

Taking software that has grown tangled over years and making it scale again — without a rewrite.

// education & certifications

2005

Started shipping software

First production code — Flash / Flex era.

2014

Technical lead, Doctors Without Borders

Selected from 1,000+ for the Ebola-response records system.

// tech stack

JavaScript

TypeScript

React

Next.js

Node.js

.NET

Java

Android

PHP

PostgreSQL

SQL Server

AWS

Git

Docker

Tailwind

~20years experience

~70shipped projects

5eras of the web

1M+views, prior site

// five eras, still writing code

2005Flash / Flex

2009PHP

2012Java / Android

2016.NET

2021React / Next · AI

// selected work

Selected work

See all ~70 projects

// accessible interactive fiction · inclusion for blind readers

Histórias do Juca

Choice-based interactive fiction, engineered to actually work with screen readers — the same adventure, alive for readers who see and readers who don't.

Accessibility-first game engine, verified against real screen readers
Decoupled a content-agnostic story engine from JSON-defined story graphs
Made every scene work hands-free and shareable out of the box

Engineered with

TypeScript

HTML

CSS

Next.js

React

View details

// nonprofit website · instituto do câncer

Instituto do Câncer Sempre Com Você

The official website for a cancer care NGO in Joinville, Brazil.

Blog with real patient stories
Monthly donation flow
Animated navigation with mobile submenu

Engineered with

TypeScript

JavaScript

HTML

CSS

Python

View details

// clinic management system · easy clinic

Easy Clinic

A full-featured medical clinic management system covering patient records, appointment scheduling, prescriptions, exam tracking, and billing analytics — built for Brazilian healthcare practices.

Full-stack reactive clinic platform
Custom clinical documentation engine
Zero-infrastructure PWA edition

Engineered with

JavaScript

HTML

CSS / LESS

Meteor

MongoDB

View details

// email marketing · CRM for direct-mail campaigns

Re@cher WebMailer

A full-fledged email marketing and CRM platform with SpamAssassin-powered spam-score pre-checks, segmented targeting, and a built-in HTML campaign editor.

Spam-score pre-flight checks
Segmented campaign targeting
Closed-loop tracking and list hygiene

Engineered with

PHP

JavaScript

HTML

CSS

MySQL

View details

// the engine

Writing

The engine. A prior site passed a million views — writing is the marketing that runs while asleep.

// writing · engineering

Crawling and self-hosting 70 dead sites

Most of ~70 shipped projects are discontinued. Here is how I crawled, archived and self-host them as honest live snapshots — and why the act of doing it is itself a craft signal.

2026-03-148 min readRead

// writing · career

Shipping across five eras of the web

Flash/Flex → PHP → Java/Android → .NET → React/Next + AI-assisted. What survives a 20-year career is not a framework — it is how you think about systems that must not fail.

2026-02-0211 min readRead

// writing · craft

On untangling systems that have grown

The engineer you want when the system actually matters — and has grown tangled. A field guide to making the messy parts scale without a rewrite.

2026-01-096 min readRead

All writing

// in their words

Testimonials

A few words from people I've built with.

Leonardo is a great professional, always eager to get to work and face challenges. He is very skilled both on frontend and backend development, as well as development processes and architecture. He is always open for work discussions, giving awesome ideas for the job in question. As a person, he is very passionate on what he does and he gives a pleasant, light and funny conversation every time we talk. I highly recommend Leonardo's work.

Thiago LPSenior Software Engineer · Worked with Leonardo on the same teaminvia LinkedIn · Apr 2020