Kamil Jakubczak, Developer in Poznań, Poland
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Kamil Jakubczak

Verified Expert  in Engineering

React Native Developer

Poznań, Poland
Toptal Member Since
September 18, 2017

Kamil is an engineer with full-stack experience and a React and React Native enthusiast who truly loves TypeScript. Kamil has experience working in big corporations, small startups, and as a solo developer—planning architecture, setting up the CI/CD, coding applications, and deploying them to a server or an app store.


Quick Check, Ltd.
Firebase, React, React Native for Web, React Native, Sass, Git, TypeScript...
Scholly, Inc.
React Native, JavaScript, Git, Redux, TypeScript, Push Notifications...
Monarch Money
React Native, JavaScript, Git, Redux, Mobile Development, iOS, Android




Preferred Environment

WebStorm, MacOS

The most amazing...

...project that I've worked on was one of the biggest eCommerce platform in Norway that has millions of daily visits.

Work Experience

React and React Native Developer

2018 - 2022
Quick Check, Ltd.
  • 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 (Objective-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 configure them so that a new client's new application could be easily created without developer input.
  • Developed native libraries for key door unlocking for hotels and added React Native bindings for them to be used within an application.
  • Added CI/CD process deployment with AppCenter instead of the manual building that was consuming much developer time. QA can build a new version on demand and set version code on their own.
  • Introduced a previously developed wallet solution for the web as a standalone SDK using React Native for Web that can be initialized for external clients in their web application.
  • Deployed apps for release on both the App Store and Google Play Store.
  • Set up deployment for web projects (wallets) with CI/CD on Bitbucket Pipelines.
Technologies: Firebase, React, React Native for Web, React Native, Sass, Git, TypeScript, JavaScript, Continuous Integration (CI), Continuous Delivery (CD), Bitbucket, Jira, Agile, Redux, CSS, Push Notifications, HTML, Unit Testing, Mobile Development, iOS, Android, Objective-C

React Native Developer

2019 - 2019
Scholly, Inc.
  • Conducted a React Native update from a legacy version to the newest available one.
  • Developed a cropper solution for camera pictures that were taken so the user could easily decide what to send for analysis.
  • Fixed issues with some screens' performance, e.g., the camera screen, which sometimes was tearing at the start.
  • Corrected the image processing and also developed screens that were correctly displaying results.
Technologies: React Native, JavaScript, Git, Redux, TypeScript, Push Notifications, Mobile Development, iOS, Android

React Native Expert

2019 - 2019
Monarch Money
  • 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 the build and started to upload them correctly to Sentry.
  • Resolved an issue with the Android build that was not working.
  • Reviewed the application to tell where some future issues might happen.
Technologies: React Native, JavaScript, Git, Redux, Mobile Development, iOS, Android

React Native Developer

2018 - 2018
Golden Era Club, Ltd.
  • Developed a whole cross-platform application from the beginning, starting from the sketches to the standalone product.
  • Suggested solutions for application development to make it easier to work with the existing API, e.g., models, mappings, model updates in future iterations, etc.
  • Proposed a successful CI/CD with Expo as the delivery method for the iterations.
  • Helped make crucial decisions regarding design and incoming features.
Technologies: Expo, Push Notifications, React Native, Git, Redux, Mobile Development, iOS, Android

React and React Native Developer

2017 - 2018
Brand Method
  • Introduced necessary back-end functions within Firebase cloud functions, e.g., analyzing breath and facial 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 it (due to legal reasons).
Technologies: Stripe, Firebase Cloud Functions, Firebase, React Native, React, Redux, Mobile Development, iOS, Android

React Native Developer

2017 - 2018
Suits & Sandals
  • Resolved before-release problems with a React Native application; also introduced Firebase tracking and performance tools.
  • Improved code quality and bottlenecks in the application and wrote down potential issues that could occur in the future due to new planned features.
  • Fixed performance and flow issues in an application regarding polls and login system.
Technologies: React Native, JavaScript, Git, Redux, Mobile Development, iOS, Android

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 (Knockout.js), Dapper, ASP.NET MVC, .NET Core, ASP.NET Web API, .NET, React Native, React, Git, Continuous Delivery (CD), Continuous Integration (CI), HTML5, Sass, Node.js, TypeScript, JavaScript, Redux, CSS, C#, HTML, Unit Testing, Mobile Development, iOS, Android

React Native Developer

2017 - 2017
Dry Good Technology, LLC
  • Developed and refactored a massive React Native application.
  • Rewrote the application to Redux in response to 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 more complex issues within a React Native app.
Technologies: React Native, Git, Redux, Mobile Development, iOS, Android

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, CSS, C#, HTML, Express.io

.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, and so on), cultural heritage (renovation), and cultural events.
  • Managed the legacy code while simultaneously creating new features.
  • Maintained contact with a client and presented changes and possible solutions to the client's requested features.
  • Introduced new technologies to more experienced developers as a way of expanding horizons.
  • Developed over 50 new forms for clients for special events that occurred yearly.
Technologies: Git, Entity Framework, Microsoft SQL Server, Knockout (Knockout.js), ASP.NET MVC, Web Forms, .NET, CSS, C#, HTML

Meta Wallet

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

Meta Restaurant App

A React Native application that can be easily customized for a new client and be released to an app store within the same day (at least uploaded to store). It is configurable with no developer input. Thanks to 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

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

Komplett Mobil

A React Native application made for one of the biggest eCommerce clients and their mobile network, the whole purpose of the application was to manage subscriptions and pay bills. It's available for both iOS and Android and needs an OIDC client as it was using ServiceIdentity for .NET Core.

Focus Pointe Global

A Focus Pointe Global application for iOS and Android with the purpose of casting votes, filling out surveys, and representing results in a clear but pleasant format. I used NativeBase as a UI tool within the application.

Facebook-like Application for Products

A mobile application that displays products that you've acquired or want to get. With this app, you can also share your products with others and get their opinions.

I 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 with a ton of features. These features included SMS/push notifications, background tasks, checking for current activity (being in a car, walking, and so on), random tests as required, scheduled tests, and confirmation of being a passenger in a moving vehicle like asking you to take pictures if there was driving activity.

Toptal Academy Lecturer | Reach Native

I had the amazing opportunity to become a Toptal Academy lecturer where I tried my very best to explain how React Native works and what new developers should be aware of.

My lectures explained the entire build process, including:
• All the necessary elements to create an application
• How to deploy them to two major app stores (Google Play and App Store)
• Firebase integrations
• Styling
• Performance improvements
• Getting the most out of a native thread
• A short comparison with other similar technologies (similar to cross-platform)
• How to start a project and how to shape the architecture that I felt comfortable with (at the time at least)
• Explained the difference between React Native alone and RN with Expo.
• Shared a few good tips 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.
2014 - 2016

Master of Science Degree in Computer Science

Poznan University of Technology - Poznań, Poland

2010 - 2014

Bachelor of Science Degree in Computer Science

Poznan University of Technology - Poznań, Poland


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


WebStorm, Git, Dapper, Expo, Bitbucket, Jira


React Native, Redux, Express.io, .NET Core, .NET, ASP.NET MVC, Knockout (Knockout.js), ASP.NET Web API


JavaScript, HTML, SCSS, CSS, C#, TypeScript, SQL, Sass, HTML5, Objective-C


Firebase, iOS, Android, MacOS


Unit Testing, Mobile Development, Continuous Integration (CI), Continuous Delivery (CD), Agile, Object-oriented Programming (OOP)


Microsoft SQL Server, MongoDB, Web Forms


Firebase Cloud Functions, Push Notifications, NativeBase

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