Jonatas Mattos

Senior full stack developer · São Paulo, Brazil

Jonatas Mattos

I've been building front-ends in React, Next.js and TypeScript for over ten years, and back-ends in Node.js and NestJS when the product calls for it. I come from game design, and it shows in how I treat interaction, feedback and performance.

Now
Full stack developer at Wescore since July 2024
Open to
Senior full stack or front-end roles, remote or hybrid in São Paulo
Education
Game design (UNIFACS) and digital games (FATEC)
Contact
jonidefjan@gmail.com

Selected work

Case studies from Wescore, an e-commerce and corporate benefits platform. The code belongs to the client, so I describe the problem, what I changed and the outcome.

7.6 sp95 image load

Slow images on the storefront

Each session loaded about 110 images, and the Chrome DevTools trace recorded 290 resources per page load. At p95, images took 7.6 s. I measured it, isolated the bottleneck and fixed it with lazy loading, Next.js Image, caching, compression and an Azure CDN, without touching the data architecture.

About 40% less data transferred per session.

88kproducts in the catalog

One catalog, many suppliers

I integrated more than 88,000 products from supplier APIs that all work differently, including Casas Bahia, Extra and Ponto Frio. Every white-label store reads that catalog in real time.

3security layers

Passed an external pentest

The platform went through an external penetration test with the protection layers I implemented.

Transport

  • HTTPS/TLS in every environment
  • CSP, HSTS and other headers
  • CORS restricted per environment

Session

  • JWT with refresh token rotation
  • OAuth2 / SSO
  • Email-based MFA

Application

  • Role-based access control
  • CSRF and XSS protection
  • Zod validation and rate limiting

80%of the storefront

One codebase, three apps

The same code powers three white-label systems. This is my share of each one:

Experience

Fourteen years across design, front-end and full stack, in e-commerce, banking, fintech and games.

Jul 2024 – now WescoreFull Stack Developer · São Paulo White-label storefront, back offices, an 88,000-product catalog, performance work, a passed pentest and continuous deployment.
Mar 2023 – May 2024 FinantechSoftware Engineer · remote, Portugal High-availability React interfaces for real-time stock market data, and REST APIs in a regulated environment.
Jun 2022 – Feb 2023 DreamShaperFull Stack Developer · São Paulo Led the migration from AngularJS to Vue.js 3 on an intellectual property platform.
Oct 2021 – Jul 2022 act digitalAngular Developer · Banco Safra Modernization of a business-critical banking application.
Jul – Oct 2019 AutbankAnalyst Programmer · Banco Crefisa React front-end built with TDD for a lending application.
2016 – 2017 Izzon EntertainmentDirector of Game Development Two Unreal Engine projects: a paintball FPS and a real-life simulator.
Aug 2014 – Oct 2021 FreelanceFull Stack Developer End-to-end web and mobile projects, from design to launch.
2012 – 2021 Agencies and studiosFront-end, webmaster and designer SHIFT INC, GoUp Digital, Elocc, Wunderman and Evolution Digital.

Tools

Front-end
React, Next.js, TypeScript, JavaScript, HTML and CSS, Tailwind CSS, shadcn/ui, Framer Motion. Also Vue.js 3, AngularJS, Bootstrap, LESS and SASS.
Web performance
Core Web Vitals, Chrome DevTools traces, lazy loading, Next.js Image, caching, compression and CDNs.
Back-end and data
Node.js, NestJS, Fastify, PHP, REST and GraphQL. PostgreSQL, MySQL and MariaDB.
Security
JWT with refresh token rotation, OAuth2/SSO, MFA, RBAC, CSRF and XSS protection, rate limiting, CSP and HSTS.
State and forms
Redux Toolkit, Context API, React Hook Form, Zod, Axios, TanStack Table.
Delivery
Git, GitHub Actions, Docker, Azure, Sentry, Jest, TDD, Scrum and JIRA.
AI in my workflow
Claude Code for pair programming, code review, refactoring and debugging; ChatGPT and Copilot for one-off tasks.
Creative
Photoshop, After Effects and Figma at work; Unreal Engine on the Izzon projects; Blender and audio from my studies.

Education

  • 2021 – ongoing
    Bachelor's in Game Design · UNIFACS
  • 2026
    Full Stack Software Development · Curso.dev
  • 2015 – 2018
    Associate degree in Digital Games · FATEC
  • 2009 – 2014
    Game Design and Digital Media · SAGA

Portuguese (native). English at B2 level, fluent in technical reading and writing.

Contact

jonidefjan@gmail.com