Przemysław Zalewski

Full Stack Web Developer from Wroclaw, Poland. My daily toolbox includes JavaScript, TypeScript, React, node.js, C#, and .NET.

I am fully committed to what I do, I am experienced with the full product lifecycle and I lead projects and teams to achieve their goals. I am product-focused, and I deliver. I love clean code, functional programming, and I participate in code reviews heavily. New challenges and opportunities are what I am looking for.

Currently working for Sandstream Development sp. z o.o.

Earliest availability from September 2024. Remote work preferred.

Learn more

Education and work experience

In 2014 I have earned a Bachelor of Science degree in Computer Science at the Faculty of Computer Science and Management of Wroclaw University of Science and Technology.

Commercial work

July 2017 - present

Sandstream Development sp. z o.o. · Senior Full Stack Web Developer · JS, React, node.js, C#

2012 - July 2017

Self-employment · 25+ apps, 3 million+ downloads · C#, XAML, ASP.NET

September - October 2014

LOSO sp. z o.o. · RatingSpeed · Windows Phone app · C#, XAML

August - September 2014

IT4Biznes Marcin Hatalak · Fast-coffee · Windows Phone app · C#, XAML

February - March 2013

Cube Investments sp. z o.o. · · Windows Phone app · C#, XAML

August 2010 - January 2011, November - December 2012

Red Dot Games · I Am Rich The Game · Windows PC, Store app · C++, C#, DirectX

September - November 2009

Red Dot Games · Platformer game engine · Windows PC, Xbox 360 · C#, XNA

Job paths

Since 2017

Full Stack Web Developer · JavaScript

2012 - 2017

Windows App Developer · C#

Before 2012

Game Developer · C++, C#


Browse my skills to see if I can fit your project’s needs.


  • JavaScript
  • TypeScript
  • C#
  • React
  • node.js
  • Redux
  • React Native
  • HTML
  • CSS
  • Sass
  • styled-components
  • Jest
  • Express.js
  • Hapi.js
  • HTTP(S)
  • REST
  • WebSockets
  • JWT
  • Server-side rendering
  • Electron
  • Expo
  • npm
  • yarn
  • Webpack
  • Babel
  • Rollup
  • ESLint
  • Prettier
  • Chrome DevTools
  • Web security
  • puppeteer
  • nginx
  • MongoDB
  • Redis
  • WebGL
  • three.js
  • .NET
  • LINQ
  • Entity Framework
  • MS SQL

Tools and soft skills

  • Git
  • GitHub
  • GitLab
  • Jira
  • Confluence
  • Figma
  • Storybook
  • Docker
  • Docker Compose
  • CI/CD
  • Jenkins
  • GitHub Actions
  • AWS
  • Google Analytics
  • Cloudflare
  • Visual Studio Code
  • Visual Studio
  • Unit testing
  • Responsive design
  • End-to-end testing
  • Scrum
  • Scrum Master
  • Agile
  • Code review
  • Mentorship


There are some notable projects I have been working on recently.

Back Office Task Management System

June 2022 - August 2022
I joined the project with a vision to lead my team in the journey of delivering the most business value while maintaining the best quality of the code and systems. I supported transition into CI/CD/CD workflows. I brought a massively refreshed UI. The changes resulted in great user feedback and a continuous reduction of errors and time waste.

PGS Software S.A. for undisclosed client


TypeScript, React, Next.js, node.js, Jest, WebdriverIO, Server-Sent Events, Web Extensions, MongoDB, styled-components, Tailwind CSS, CSS, REST, Auth0, Kubernetes, Datadog, Jira, CircleCI

My responsibilities
  • I was responsible for the technical leadership of a team of 4 developers while also performing active development of features. My day-to-day work included bringing improvements to existing systems and swift communication within the team and across the organization. Through active and deep code review participation, I encouraged my fellow team members to follow best practices and reduce technical debt. I led many fruitful discussions and technical meetings to align on common team values. I steered the development into a data-driven and short-feedback loop and maintained the backlog and sprint plans. I have undergone massive decoupling and simplification efforts to keep the repositories maintainable. By keeping a tight eye on security and correctness, I enforced strict auth, improved observability, and logging. I participated in the cloud cost reduction process by aligning the resource usage for deployments and optimizing for performance.
  • Ads and Ancillaries
    July 2021 - May 2022
    I worked closely with other developers, product managers, designers, and stakeholders to deliver the best ad experience and coverage across multiple touchpoints and platforms (web, mobile apps, email). I delivered new features while making huge improvements to existing code and processes. Even when my role was mainly on the frontend, I was always happy to jump in and get my hands dirty with server-side code or initially unfamiliar areas such as native code in mobile apps.

    PGS Software S.A. for Omio


    TypeScript, React, JavaScript, node.js, React Native, Jest, Storybook, Hapi.js, REST, Redux, Swift, Kotlin, go, Java, Redash, SQL, BigQuery, Kibana, Grafana, Amplitude, Google Ad Manager, Firebase, Xcode, Android Studio, Jira, Confluence

    My responsibilities
  • I was responsible for bringing the requested features to life, actively participating in the full life cycles from idea and design discussion to implementation, A/B testing, monitoring, and continuous improvement. I consistently got rid of technology debt, improved performance and kept services and features secure and up to date. I loved doing quick, deep, and helpful code reviews. I was always there when any help was needed. During this project, I actively participated in regular meetings and cross-team technical groups to share and disseminate knowledge. I maintained close collaboration with my colleagues during joint programming sessions in pairs and larger groups.
  • Undisclosed

    July 2017 - June 2021
    Web application for rendering, manipulation, and storage of 3D scans from profilometers, AFMs, and other 3D microscopes. A bespoke solution for a leading company that manufactures profilometry devices and is focused on thin-film measurements.

    Sandstream Development sp. z o.o. for undisclosed client


    JavaScript, React, Redux, Redux Thunk, node.js, Jest, C#, .NET Core, Entity Framework, MySQL, ASP.NET Core, Sass, WebGL, three.js, Git, GitHub, Webpack, puppeteer, Expo, React Native, Storybook, APM (Azure Application Insights), AWS, Stripe

    My responsibilities
  • I was responsible for full-stack software development using a React-based frontend with a C# backend to provide a web-based app that allows 3D image visualization and processing. During this project, I have learned how to work with an on-site and remote team to deliver a great product that satisfies client’s and users’ needs. I had gained experience with git workflow and collaboration with other developers. I had been performing code reviews and delivered high-quality code. I had also been responsible for the integration of external libraries and close cooperation with the APIs provider, which often resulted in a need for providing detailed bug reports and test cases. I’ve been continuously focused on providing great user experience, performance, and security, which is why I have brought in useful solutions like visual regression detection toolkit, secret leakage prevention, and optimized the build process to yield the optimal bundle and improve development experience.
    January 2019 - present
    In-house multiplatform SaaS time tracking system to improve workflows of creative people. With automatic time tracking and integrations, it makes all the parties involved in projects credible and accountable.

    Sandstream Development sp. z o.o.


    JavaScript, React, node.js, Express.js, Sass, styled-components, Webpack, Docker, Docker Compose, nginx, MongoDB, mongoose, Redis, JWT, CI/CD, Jenkins, Git, GitLab, ELK Stack, puppeteer, Expo, React Native, Electron, Storybook, APM (, Amazon S3, paddle

    My responsibilities
  • I was responsible for leading the project starting from creating the project vision, defining the microservices-based architecture powered by Docker containers, then by delivery of an MVP and continuous development of new features. During this project, I have also been performing a Scrum Master role and helped my teammates to deliver the desired product that meets users’ and stakeholders’ needs. I was responsible for setting up continuous integration, delivery, and deployment to shorten iteration and delivery cycles. I have introduced an end-to-end testing solution to maintain high quality and reduce risks of broken deployments. I have managed to get the app to multiple platforms and app stores (Windows, macOS, Linux, Windows Store, Mac App Store, Chrome Extension, Android, iOS) by using cross-platform tools like Electron and React Native. I was responsible for the external payment system integration and setting up a subscription model.
  • Validator


    November 2019 - December 2019
    Mobile app to help users capture perfect photos for ID documents. The app was submitted to the Polish government competition, GovTech, and scored 5th place.

    Sandstream Development sp. z o.o.


    JavaScript, React, TensorFlow, TensorFlow Lite, face-api.js, OpenCV, WebAssembly, Android, Kotlin, Git, GitLab

    My responsibilities
  • I was responsible for leading a small team to deliver a fully functional app that meets the competition’s requirements within a tight deadline. I have incorporated AI-based solutions and libraries to tackle the problem with near-real-time performance in mind. I have integrated React-based frontend with native Kotlin-based Android app that ran bare-metal models for extended performance on mobile, while still being able to run the app entirely on the web, fully offline. I have implemented a complex image detection and processing pipeline using face-api.js, OpenCV, TensorFlow, and custom functions. To achieve proper results, I have provided an extensive test suite, debug and visualization tools, and gathered a huge set of samples. Finally, I wrote a submission paper with a detailed report and documentation.
  • October 2019 - August 2020
    Modern library of statically-typed modular functions for daily use in JavaScript and TypeScript projects. It served as a place to sharpen my TypeScript skills. Extensively used across the company’s projects.

    Sandstream Development sp. z o.o.


    TypeScript, JavaScript, Rollup, Static site generators, Git, GitHub, GitHub Pages, GitHub Actions, React, node.js, Babel, Prettier, ESLint

    My responsibilities
  • I was responsible for providing a library to reduce code duplication across the company’s repositories. I have defined module boundaries and extracted a huge chunk of utility functions to be strongly typed and included within the library. I wrote hundreds of TypeScript functions and I have covered them with tests to attain full coverage. I have been responsible for the package releases on npm and related chores. I have been performing code reviews to make sure the shared code is of high quality. With the custom static site generation toolkit, I have provided searchable and interactive documentation.
  • Korona Krulów

    Korona Krulów
    A game about COVID-19, polish government, and propaganda.

    JavaScript, React, node.js, nginx

    My responsibilities
  • I created and deployed a React-based game played by hundreds of thousands of people. I have managed to publish the game within two weeks of work. The game included over 400 actions and their effects that impact the internal simulation of infections and economy and society. I have implemented a leaderboards system to make the game more competitive.
  • Driving licence tests

    Driving licence tests
    Responsive web app to prepare for the polish driving theory test exam.

    JavaScript, React, node.js, Babel, ESLint, Visual Studio Code, MobX

    My responsibilities
  • Writing the front-end with React.js, styling with CSS, designing responsive, mobile-friendly views
  • Database design and implementation of static data as a code modules system
  • Open-sourcing test questions and explanations along with an edit system based on Git
  • Implementing reactive view model using MobX and performance testing
  • Enabling server-side rendering using node.js on IIS with iis-node
  • Promegle

    Anonymous chat application for Windows Phone and web.

    C#, JavaScript, React, node.js, Babel, Redux, WebSockets, Docker, ASP.NET, Windows Phone, Windows Store

    My responsibilities
  • Writing the front-end with React.js, Redux, and a custom styling solution
  • Implementing message queue system and reactive immutable database solution
  • Implementing video calling over WebRTC along with the signaling server
  • Automatic image classification using Yahoo’s Not Safe For Work deep neural model running on Docker
  • Integrating with legacy ASP.NET long polling back-end servers and C# code
  • Personal web page and blog

    Personal web page and blog
    A static site with a personal blog and resume.

    JavaScript, React, node.js, Babel, ESLint, Git, GitHub, Visual Studio Code, Webpack

    My responsibilities
  • Writing the front-end with React.js, styling with CSS, using data as a code modules
  • Designing responsive and printable resume page
  • Static blog generation and integrating Disqus commenting system
  • Controlling source code and data versions using Git
  • Deploying server-side rendering with express.js with iss-node on Windows IIS
  • Store ᴾᴿᴼ

    Store ᴾᴿᴼ
    A Windows Phone application with redesigned and rethought store interface.

    C#, XAML, MVVM, ASP.NET, MS SQL, Visual Studio

    My responsibilities
  • Design and development of Windows Phone 8 application using C#, XAML, and MVVM pattern
  • Creating and deploying ASP.NET based web service and API endpoints along with a landing page
  • Designing and managing MS SQL database and integrating it with back-end service using Entity Framework
  • Back-end crawling services for deals discovery and sending push notifications
  • Internationalization implementation for over 192 languages
  • Deployment of multiple updates, maintenance work, and customer support
  • MusicTube

    Windows Phone, Windows Store, Web App for music videos playback from YouTube.

    C#, XAML, MVVM, ASP.NET, MS SQL, Visual Studio

    My responsibilities
  • YouTube and APIs integration
  • Windows Store, Windows Phone and web app development using C#, XAML, MVVM, ASP.NET
  • Design and management of MS SQL database along with crawling services
  • Monetization through multiple ad networks
  • Implementation of multi-platform shared code solution
  • Deploying multiple updates, maintenance work and customer support
  • Pogaduszki


    Windows Phone messenger application of Gadu-Gadu protocol.

    C#, XAML, MVVM, ASP.NET, MS SQL, Visual Studio

    My responsibilities
  • Development of native Windows Phone
  • Implementation of Gadu-Gadu binary protocol
  • Setting up a persistent proxy and push notification server
  • Deploying multiple updates, maintenance work, and customer support


    A streaming app of Polish public TV channels for the final studies project. Made in collaboration with Grzegorz Ślązak, Justyna Witkowska and Paweł Skiba.

    C#, XAML, MVVM, ASP.NET, MS SQL, Visual Studio

    My responsibilities
  • Collaborative development of native Windows Store and Windows Phone applications
  • Deployment of ASP.NET based streaming services and API endpoints
  • Development of streaming protocol with various bitrates
  • Designing chunked stream format which allows history playback
  • Deploying streamer app along with hardware wiring and antennas using DVB-T adapters
  • feed viewer application for Windows Phone.

    Cube Investments sp. z o.o.



    My responsibilities
  • Development of Windows Phone application based on client’s provided project using XAML, MVVM, and C#
  • Integration with existing web APIs
  • Collaboration with the project owner and the rest of the team
  • Monetization through different ad networks
  • Deploying multiple updates after the release
  • RatingSpeed


    Network speed measurement app for Windows Phone.

    LOSO sp. z o.o.



    My responsibilities
  • Development of Windows Phone application using XAML, MVVM, and C#
  • Implementing network speed measurement, test results statistics, and upload
  • Implementing the design provided by the client
  • Preparing the app for publishing in the Windows Store and providing app updates
  • Fast-coffee


    Windows Phone dating app.

    IT4Biznes Marcin Hatalak


    C#, XAML, MVVM, ASP.NET,, Visual Studio

    My responsibilities
  • Implementing real-time chatting with
  • Implementing chat list, chat and profile views
  • Integrating with provided APIs
  • Working closely with the development team
  • I Am Rich The Game

    I Am Rich The Game

    Windows PC and Windows Store turn-based simulation game.

    Red Dot Games


    C++, XAML, C#, DirectX 9, DirectX 11, Visual Studio

    My responsibilities
  • Development of native Win32 game in C++ with a DirectX renderer
  • Networking protocol with Winsock, supporting up to four players
  • Implementation of provided game design and assets
  • Porting to Windows Store as hybrid native and C# app
  • Deploying to the app store and providing updates
  • Platformer game engine

    Platformer game engine

    Windows PC and Xbox 360 platformer game engine with a built-in editor.

    Red Dot Games


    C#, DirectX 9, XNA, Visual Studio

    My responsibilities
  • Development of XNA game engine
  • Creation of game editor with support for live play
  • Implementation of various game mechanics
  • Your next project can be here

    See more

    Interests and future goals

    I am always ready to learn new things and explore new opportunities.

    My interests

    • Functional programming
    • Language design
    • Deep neural networks
    • UX
    • App development
    • DX
    • Security
    • Performance
    • User interface design
    • Dogs 🐶

    Functional programming, language design, deep neural networks, UX, app development, DX, security, performance, user interface design, dogs 🐶.

    My goals

    • Set up a Kubernetes cluster
    • Learn Haskell well
    • Give a speech about programming
    • Join a team of highly-skilled and experienced people
    • Improve my spoken English
    • Sharpen my TypeScript skills
    • Contribute to an open source project
    • Write more tests and explore TDD approach
    • Increase presence on StackOverflow

    Set up a Kubernetes cluster.

    Wyrażam zgodę na przetwarzanie moich danych osobowych dla potrzeb niezbędnych do realizacji procesu rekrutacji (zgodnie z Ustawą z dnia 29.08.1997 roku o Ochronie Danych Osobowych; tekst jednolity: Dz. U. 2016 r. poz. 922).

    Download this resume as a PDF

    Source code available on GitHub. Background images from