Products that are live,not prototypes.

Gusthavo Rangel, full stack developer in Sorocaba, Brazil. Backend, web, mobile and the infrastructure that keeps it all running: fintech, ERP, marketplaces and apps on the stores.

See the products liveLinkedIn
10+
systems in production
3
apps on the app stores

8 products I built that are live today.

From the database to the app on the store: the architecture, code and operations of each one went through my hands. Drag to browse.

  • MD FácilSaaS product1/8

    MD FácilCash-flow fintech

    Banks connected through Open Finance, automatic reconciliation, PIX and card billing, Brazilian service invoices and an AI copilot that explains the numbers in plain language.

    Next.js, Fastify, Drizzle, PostgreSQL, BullMQ, Open Finance, Asaas

  • KonkretoCustom build2/8

    KonkretoPaving-works management

    Foremen log the day in the app even without signal; the office follows the job street by street and issues the measurement report in the city hall's format.

    NestJS, oRPC, Next.js, Expo, PostGIS, offline-first

  • TaguSaaS product3/8

    TaguLabel printing through an API

    One HTTP call becomes a ZPL label on a Zebra or a PDF on a laser printer. Lightweight Rust agent for Windows with a local queue and auto-update.

    Rust, Bun, Hono, Next.js, PostgreSQL

  • TranquilizzaCustom build4/8

    TranquilizzaHome-maintenance subscription, 2 apps on the stores

    Customers register appliances, open tickets and track the technician; technicians get their own app (Tranquilizza Pro) with schedule and visits.

    Fastify, oRPC, Expo, TanStack Start, PostgreSQL

  • NexobiSaaS product5/8

    NexobiAI-powered BI

    Connects data sources, builds interactive dashboards, lets you chat with your data and generates dashboards automatically.

    NestJS, Next.js, Tauri, pgvector, PostgreSQL

  • RAQ ONECustom build6/8

    RAQ ONERacket-sports marketplace, app on the stores

    Buy and sell rackets and gear with identity verification, real-time chat, payments and shipping.

    Fastify, Expo, PostgreSQL, Redis, WebSocket

  • TrappiCustom build7/8

    TrappiAdvertising inside ride-hailing cars

    Seat-back tablets, fleet management, playlists, impression analytics and real-time monitoring. Backend in Go.

    Go, Next.js, Flutter, PostgreSQL, Redis

  • QuitutePersonal project, open source8/8

    QuituteSales notebook for home bakers

    Recipe cost sheets that re-price when ingredients go up, store credit, orders and cash. Works offline.

    Expo, Hono, Cloudflare Workers, Drizzle, SQLite

Fixed-scope projects, delivered to production.

What I do as a freelancer, to the same standard as the products above: defined scope, deployment and documentation.

Also available on WhatsApp and 99freelas (Brazil). I reply within one business day.

  • Brazilian tax integrations

    Issuing and querying NF-e and NFS-e invoices, SEFAZ and Focus NFe. From registration to an authorized invoice, with rejection handling.

    NF-eNFS-eSEFAZ

  • Open Finance and payments

    Bank connections with Pluggy or Lina, automatic reconciliation, PIX, boleto and card billing with Asaas, reliable webhooks.

    PluggyAsaasPIX

  • ERP integration

    Middleware between ERPs (Tiny and others) and third-party systems: queues, retries, an operations panel and automated reports.

    Tiny ERPn8nwebhooks

  • SaaS and apps from scratch

    Multi-tenant MVP in TypeScript, offline-first mobile app published on the stores and infrastructure with automated deploys.

    TypeScriptExpoDocker

Who builds it.

Gusthavo Rangel
Gusthavo Rangel VieiraSorocaba, Brazil (UTC−3)

I build SaaS products and custom systems from zero to production. Today that is more than ten systems live that I developed and maintain: fintech, AI-powered BI, construction management, home maintenance, marketplace, technical assistance and digital media.

I work mostly in TypeScript on PostgreSQL and Redis, with DDD, contract-first APIs and monorepos. When the problem calls for it, I leave JavaScript: Go, Rust, Python and Flutter. And I run the infrastructure behind these products.

Role
Mid-level Full Stack Developer
Education
Systems Analysis and Development, FATEC Sorocaba
Engagement
Contractor or employee, remote or hybrid
  • BackendNestJS, Fastify, Hono, Go
  • WebNext.js, React, TanStack
  • MobileReact Native, Expo, Flutter
  • DataPostgreSQL, Redis, Drizzle, pgvector
  • InfraDocker, Traefik, GitHub Actions, VPS

Shall we put your product live?gusthavorangel@gmail.com

A role, a project or a technical question. I reply within one business day.