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Tomasz Piotr Stefaniak, Software Developer in Rio de Janeiro - State of Rio de Janeiro, Brazil
Tomasz Piotr Stefaniak

Software Developer in Rio de Janeiro - State of Rio de Janeiro, Brazil

Member since May 19, 2017
Tomasz is a Full-stack Engineer passionate about web development. He specializes in JavaScript frameworks (Node.js, Express.js, ReactJS, Redux, Vue.js etc). Before joining the JavaScript ecosystem, he developed iOS and Android apps. Tomasz has worked in teams as well as on solo projects and knows the importance of good communication. Having studied in London at a world top 10 university, he's very comfortable with the English language.
Tomasz is now available for hire


  • Blackjack Apprenticeship
    React, React Router, Redux, Redux Saga, Recompose, Sass, Webpack, CSS Modules
  • GLO
    Shopify, Shopify Liquid, HTML, CSS, jQuery, Zeplin
  • Freelance
    React, React Router, Redux, Node.js, Less, Webpack, Heroku


  • React, 3 years
  • JavaScript, 3 years
  • CSS3, 2 years
  • Redux, 2 years
  • Node.js, 2 years
  • React Router, 2 years
  • Redux-saga, 1 year
Rio de Janeiro - State of Rio de Janeiro, Brazil



Preferred Environment

OS X, Git, Sublime

The most amazing...

...thing I've coded was a map of psychological profiles of different London boroughs based on 200,000 geolocated tweets analysed with IBM Watson API.


  • React Developer

    2017 - PRESENT
    Blackjack Apprenticeship
    • Built a fully functional Blackjack simulator with React. This included four training modules, a simulated game, and a test-out mode, with multiple gameplay settings for each one.
    • Adapted create-react-app's Webpack configuration to use CSS modules.
    • Adapted create-react-app's Webpack configuration to embed all image assets as data URLs.
    • Worked with Redux Saga to manage complex gameplay flows.
    Technologies: React, React Router, Redux, Redux Saga, Recompose, Sass, Webpack, CSS Modules
  • Front-end Developer (via Toptal)

    2018 - 2018
    • Used Jumpstart as the foundation of a brand-new theme commissioned by the client.
    • Built over a dozen flexible sections to allow the client to customize the content and feel of the website.
    • Created mobile and desktop versions of each element and adjusted for tablet-size devices where necessary.
    • Put on my designer hat and created mobile versions of the elements where only the desktop design was provided.
    • Coordinated with the client on a daily basis and at a weekly basis with the lead designer.
    Technologies: Shopify, Shopify Liquid, HTML, CSS, jQuery, Zeplin
  • React & Node.js Developer

    2018 - 2018
    • Created a plan for how to adapt the front-end of an open source blockchain application to be used by the client's custom blockchain.
    • Documented the front-end of the open-source application so that more junior developers could work with it and be productive from day one. This included documenting the main React components, the unit tests, the deployment of the application, the SSR server, and code style guides/linters.
    • Redesigned the UI of the application to provide a distinctive feel consistent with the client's brand.
    • Built a simple HTML/CSS landing page for the project and deployed to Firebase, a host that best matched the client's needs.
    Technologies: React, React Router, Redux, Node.js, Less, Webpack, Heroku
  • Front-end Engineer

    2017 - 2018
    Operadores Turísticos Internacionales S.A. (via Toptal)
    • Created a customer-facing service for viewing and booking tours, hotels, and transfers of different types using interactive maps built with Mapbox.
    • Used a complex API provided by the client and created a Redux Saga structure for managing chains of API calls.
    • Built the React components using Recompose library to clearly separate the presentation and the logic parts of the components.
    • Created a Redux Saga structure for managing search filters to make all the relevant data from various components accessible in a single store.
    • Used Airbnb-inspired modular SCSS with BEM to create style sheets that are both easy to understand and modify.
    • Used the library Prettier with pre-commit hooks to ensure the code formatting is kept consistent in all .js, .jsx and .scss files.
    Technologies: Mapbox, React.js, Redux, React Router, Redux Saga, Recompose, SCSS
  • Co-founder, Full-stack JavaScript Developer

    2016 - 2017
    • Created an interactive map of independent fashion design/gourmet food producers in Rio de Janeiro as an MVP of an online marketplace platform using Meteor, MongoDB, and React.js.
    • Created a complex producer-facing dashboard for managing products, orders and money withdrawals as a front-end developer. This included a complex gallery feature and a Shopify-inspired system for creating multiple product variants with different colors/sizes/materials, etc.
    • Created a quick setup service with six steps (breadcrumbs) to ensure all new sellers have their profiles completely filled in and have at least one product to sell before they are approved on the marketplace.
    Technologies: Meteor, React.js, Redux, React Router, SCSS, ES6, MapBox, MongoDB
  • Project Manager

    2015 - 2016
    NUMA Paris
    • Supported the Startup Accelerator team as a Project Manager in processing and analyzing applications.
    • Analyzed past application data and created tools for internal use, such as a searchable database of startups or a tool for startup evaluation.
    • Organized the kick-off event for a new startup class.
    Technologies: PHP, HTML, CSS, Meteor, React.js
  • iOS Developer, Co-founder

    2014 - 2015
    Ocean London
    • Co-founded Ocean while still studying at UCL.
    • Implemented a recommendation algorithm by analyzing the user’s psychological profile using a version of the Big Five Personality Test and employing a linear regression algorithm and a rating system to map psychological profile to particular preferences. For example, what’s the probability that a user with high openness score will like a restaurant given that it’s been described as "underground"?
    • Designed the algorithm that governed the app and together with other developers built the mobile app in Swift.
    Technologies: Objective-C, Swift, Xcode


  • Panda HSK (Development)

    Panda HSK is Chinese learning app that I've both designed and coded. It offers three study modes for practicing the words and phrases that appear in the HSK 1 Chinese exam. It's built with React Native, Redux, and TypeScript.

  • Emojify 🎉 (Development)

    Emojify was an emoji-based URL shortener. It let you shorten links using one of 75 single-emoji domains such as http://🦍.tk, http://🍾.cf, http://🍹.cf etc. It was featured on the front page of Product Hunt.

    It was built with React.js with React Router for the front-end. On the back-end, it used Node.js with Express.js and Mongoose. It offered 75 different domains and was hosted on Google Cloud buckets.

  • Bazzah Producer Panel (Development)

    Bazzah is an online marketplace for independent fashion producers. The producers use the panel to manage their stores with the ability to add and edit products, product images, and prices. Users can also edit store description, logo, and cover image as well as see their account balance and request the withdrawal of funds.

  • Chilla (Development)

    Build a location-based news app with React Native, allowing users to create photo stories and others to react to other users' stories with emoji. Used Node.js with Mongoose and MongoDB with geo queries for the back-end and implemented anonymous user accounts with Passport.js and Firebase.


  • Languages

    CSS3, JavaScript, SCSS, HTML5, TypeScript, Swift
  • Frameworks

    Redux, React Native, iOS SDK, Express.js
  • Libraries/APIs

    React, Liquid, React Router, Node.js, Vue.js, Redux-saga, LeafletJS
  • Tools

    Adobe Illustrator, Mongoose
  • Paradigms

    BEM, Agile
  • Platforms

    Shopify, iOS, Meteor, MapBox
  • Other

  • Storage



  • Bachelor's degree in Arts and Sciences: Sciences and Engineering
    2012 - 2015
    University College London (UCL) - London
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