Kamil Jakubczak, Software Developer in Poznań, Poland
Kamil Jakubczak

Software Developer in Poznań, Poland

Member since June 17, 2017
Kamil is a React, React Native, and JavaScript enthusiast (with a small dose of .NET experience). He recently became hooked by mobile development, deployment, and whatever is needed for it, mostly due to React Native being superb and fun to work with.
Kamil is now available for hire




Poznań, Poland



Preferred Environment

VS Code, WebStorm, Git, MacOS

The most amazing...

...thing I've developed is a mobile app from zero to deployment within three weeks with payments and native calendar integration.


  • React and React Native Developer

    2018 - PRESENT
    Quick Check, Ltd. (via Toptal)
    • Refactored an application due to issues with performance and looming bottlenecks.
    • Developed new features in the app, e.g., Google Maps, Apple Pay/Google Pay, location based results, or opening a hotel room using NFC.
    • Reworked a wallet into a React Native solution instead of using separate iOS (Obj-C) and Android (Java) versions.
    • Implemented new check-in solutions for restaurants and hotels using React Native.
    • Created tooling necessary to easily add new assets and config so the new application for a new client can be easily created without developer input.
    • Developed native libraries for key door unlocking for hotels and added React Native bindings for them so they can be used within an application.
    • Took care of necessary React Native updates, successfully updating firstly to version 0.57, later to 0.59, and finally -0.61.
    • Added CI/CD process deployment with AppCenter instead of manual building which was consuming a lot of developer time. QA can build a new version on demand and set version code on their own.
    • Introduced a previously developed wallet solution to web as a standalone SDK using React Native for Web that can be initialized for external clients in their web application.
    • Started a new wallet version with many improvements, thanks to lessons learnt from previous version, e.g., smaller package size due to replacement of React Native for Web with React.
    • Set up deployment for web projects (wallets) with CI/CD on Bitbucket pipelines.
    • Created an example app that shows all possible configurations for a new wallet SDK where the user can change all options independently and see how it will look in real time.
    • Deployed apps for release on both the App Store and Google Play Store.
    Technologies: Firebase, React, React Native for Web, React Native
  • React Native Developer

    2019 - 2019
    Scholly, Inc. (via Toptal)
    • Conducted a React Native update from a legacy version to the newest one that was available.
    • Developed a cropper solution for camera pictures that were taken so the user could easily decide what to send for analyzing.
    • Fixed issues with some screens' performance; e.g., the camera screen, which sometimes was tearing at the start.
    • Corrected image processing and also developed screens that were correctly displaying results.
    Technologies: React Native
  • React Native Expert

    2019 - 2019
    Monarch Money (via Toptal)
    • Conducted React Native update from 0.59 version to 0.60.x.
    • Introduced CodePush to allow over-the-air app updates.
    • Fixed source map generation during build and started to upload them correctly to Sentry.
    • Resolved an issue with the Android build that wasn't working.
    • Reviewed the application to tell where some future issues might happen.
    Technologies: React Native
  • React Native Developer

    2018 - 2018
    Golden Era Club, Ltd. (via Toptal)
    • Developed a whole cross-platform application from beginning (from sketches to standalone product).
    • Suggested solutions for application development, to make it easier to work with the existing API (models, mappings, model updates in future iterations, etc.).
    • Proposed successful CI/CD with Expo as a way to deliver iterations.
    • Helped make crucial design decisions.
    Technologies: Expo, Push Notifications, React Native
  • React and React Native Developer

    2017 - 2018
    Brand Method (via Toptal)
    • Implemented new register flow.
    • Introduced necessary back-end functions within Firebase cloud functions (analyzing breath, face recognition).
    • Implemented background tasks in the application for checking user activities (walking/driving) in intervals/if there is a request for the user to take a test.
    • Added a scheduling system by introducing cron jobs with Firebase cloud functions.
    • Included a breath analyzer in the application and created React Native bindings for native SDKs.
    • Introduced a face recognition API to be sure that the user, in fact, is the one that is supposed to use (due to legal reasons).
    Technologies: Stripe, Firebase Cloud Functions, Firebase, React Native, React
  • React Native Developer

    2017 - 2018
    Suits & Sandals (via Toptal)
    • Resolved some before-release problems with a React Native application.
    • Added Firebase tracking and performance tools.
    • Improved code quality and bottlenecks that happened here and there.
    • Prepared necessary pre-release items.
    • Fixed performance and flow issues in an application regarding polls and login system.
    Technologies: React Native
  • Full-stack Developer

    2016 - 2018
    • Took a leading role in introducing new technologies within new projects and existing ones.
    • Created new applications from proof of concept to regular apps and made decisions regarding tooling in the front end.
    • Improved the possibility of using .NET Core within the company by introducing improvements to CI/CD.
    • Analyzed client requirements and maintained multiple production applications.
    • Created the first mobile application within the whole company, using React Native, which was really well received by its customers.
    • Created pipelines for CI/CD for mobile development from scratch.
    • Helped colleagues with complicated or performance issues in a front-end environment.
    Technologies: Knockout.js, Dapper, ASP.NET MVC, .NET Core, ASP.NET Web API, .NET, React Native, React
  • React Native Developer

    2017 - 2017
    Dry Good Technology, LLC (via Toptal)
    • Developed and refactored a massive React Native application.
    • Rewrote the application to Redux in response to some performance issues, and refactored significant portions of the rest.
    • Prepared complex animations that were necessary for the application (e.g., shared element transition).
    • Assisted the client with future features and methods for solving some more complex issues within a React Native app.
    Technologies: React Native
  • Full-stack Developer

    2015 - 2016
    Sputnik Software
    • Developed an application for the government where you could apply for state funds. It was also the very first application in the company that replaced Knockout with React, where React later became a core library for the company.
    • Started the development of new microservice-based architecture with Docker and Node.js.
    • Created a company identity system as a microservice for other services using Node.js and OrientDB.
    • Created a CMS with a Node.js-based back end and React-based front end that was presented to clients, as an evolution of the current solution.
    • Led one of the R&D teams and analyzed client requirements.
    • Planned a solution for two big government institutions for sharing customers and keeping them in sync.
    Technologies: ASP.NET MVC, ASP.NET Web API, Microsoft SQL Server, Git, JavaScript, MongoDB, SCSS, React, .NET, Node.js
  • .NET Developer

    2013 - 2015
    Sputnik Software
    • Supported a big platform that included a few applications used by citizens to apply for government funding for cultural projects (movies, literature, etc.), cultural heritage (renovation), and cultural events.
    • Managed legacy code while simultaneously creating new features.
    • Kept contact with a client and presented changes and possible solutions of requested features from the client.
    • Introduced new technologies to more experienced developers as a way of expanding horizons.
    • Developed 50+ new forms for clients for special events that occurred yearly.
    Technologies: Git, Entity Framework, Microsoft SQL Server, Knockout.js, ASP.NET MVC, Web Forms, .NET


  • Meta Wallet

    Meta Wallet is an SDK for clients that allows you to set a new wallet anywhere. It is configured though JSON options that are fetched from S3, it allows custom fonts, custom appearance, setting alternative dgiital payments as well as classic credit card systems.

  • Meta Restaurant App

    React Native application that can be easily customized for new client and be released on store within same day (at least uploaded to store). It is configured with no developer input; with a changing application key, we can fetch the configuration for a specific new application as well as assets, icons, fonts, and anything else necessary for a new application, and put all of it in the new build (including package name and version for the store).

  • OIDC Client for React Native

    ODIC client for Hybrid workflow: one to one with specifications. It also had single sign-on included as the same authentication service was used for some web app. For that to work, Chrome Custom Tabs and Safari Browser were used (instead of WebView due to lack of cookies that exist in regular browsers and security concerns).

  • Komplett Mobil

    React Native application made for one of biggest eCommerce clients and their mobile network. Available for both, iOS and Android. It used OIDC client as it was using ServiceIdentity for .NET Core.

  • FPG

    Front Pointe Global application for iOS and Android; an application whose whole point is to cast votes and show them in a pleasant format. Native Base is used as a UI tool within the application.

  • Facebook-like Application for Products

    Mobile application which was displaying products that you acquired or wanted to get. You could also share your products with others and see their opinions. Introduced a kind of gamification, where you could see other people's stuff and tell who is the "trendsetter" and such.

  • Breathalyzer Application

    A mobile application that worked with a breathalyzer. It had push notifications, background tasks, checking for current activity (being in a car, walking, etc.), SMS notifications, asking you to take pictures if there was driving activity (to ensure that you were a passenger), random tests as required, or scheduled tests.

  • Toptal Academy Lecturer

    Experienced amazing opportunity to be a Toptal Academy Lecturer where I tried my very best to explain how React Native works and what new developers should be aware of. Lectures explained whole building process, all necessary elements to create an application and put it on two major stores (Google Play and App Store), Firebase integration, styling, performance improvements, and getting the most out of a native thread. There was a short comparison with other similar technologies (similar to cross-platform). I explained how to start a project and how I shape the architecture that I feel comfortable with (at the time at least). I explained the difference between React Native alone and RN with Expo. Finally, I shared a few good ideas and lesser-known hints about React Native.

  • CeraCare App

    React Native application for care workers, to make it easier for them to work with patients, to have information about each patient (as patient could vary daily) and to keep everything in check and control. It was also a way to know for family of patients, on how their loved ones are feeling.

  • React Tutorial: Components, Hooks, and Performance (Publication)
    In recent years, React has established itself as the most popular library in the JavaScript universe. However, rather than rest on its laurels, the React team is still working hard to make it better. In the second part of our React tutorial series, Toptal JavaScript Developer Kamil Jakubczak takes a closer look at some of its features, including hooks, the latest addition to React.
  • React Tutorial: How to Get Started and How it Compares (Publication)
    In recent years, React went from being an also-ran in the JavaScript universe to the most popular JS library. However, how does React stack up against Angular and VueJS in 2019? In the first part of our React tutorial series, Toptal JavaScript Developer Kamil Jakubczak outlines the reasons behind React’s popularity and explains how to get started on your first React app.


  • Languages

    JavaScript, HTML, SCSS, CSS, C#, TypeScript, SQL
  • Frameworks

    React Native, Redux, Express.io, .NET Core, .NET, ASP.NET MVC, Knockout.js, ASP.NET Web API
  • Libraries/APIs

    React, Node.js, Entity Framework, Stripe, React Native for Web
  • Tools

    WebStorm, Zeplin, Git, VS Code, Dapper, Expo
  • Paradigms

    Functional Programming, Agile Software Development, Asynchronous Programming, Object-oriented Programming (OOP), Unit Testing, Mobile Development
  • Platforms

    Firebase, iOS, Android, MacOS
  • Storage

    Microsoft SQL Server, MongoDB, Web Forms
  • Other

    Firebase Cloud Functions, Push Notifications


  • Master of Science degree in Computer Science
    2014 - 2016
    Poznan University of Technology - Poznań, Poland
  • Bachelor of Science degree in Computer Science
    2010 - 2014
    Poznan University of Technology - Poznań, Poland

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