Jurek Wozniak, Developer in Warsaw, Poland
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Jurek Wozniak

Verified Expert  in Engineering

Front-end Architecture Developer

Warsaw, Poland
Toptal Member Since
December 20, 2021

In the most recent times, Jurek has worked for an LA-based startup as a front-end contractor. This work included creating apps, working on the architecture, and introducing the best modern patterns and technologies. Jurek is also a coding mentor and released a best-selling RxJS course on Udemy. Jurek is currently looking for new challenges.


Angular, NgRx, RxJS, Unit Testing, Software Architecture
C#.NET, ASP.NET MVC, MongoDB, AngularJS, JavaScript, SCSS
Angular, RxJS, TypeScript, Microservices




Preferred Environment

Windows, MacOS

The most amazing...

...thing I've made was an app that allows users to design graphics in a PowerPoint-like style, which was populated with API data and presented on remote screens.

Work Experience

Lead Software Developer

2018 - 2021
  • Worked for a digital signage startup, which gained dozens of Fortune 500 customers and eventually got merged.
  • Designed, led, and implemented numerous projects. The most significant is an app allowing users to edit templates in PowerPoint-like style and then feed the templates with data coming from an API, a spreadsheet, or the data view inside of the app.
  • Designed and led the implementation of a system that handled translations in an automated way. Investigated the available solutions and chose the ones which fit our needs best. I prepared the tools for developers and translators.
  • Designed and implemented a feature-packed file uploader. Users can upload files and images from cloud sources, like Pixabay, Google Drive, OneDrive, Box, and Dropbox. The uploader encoded the files in the background and included solid error handling.
  • Increased reliability by unifying and expanding the reusability of components across the platform.
  • Researched and implemented automated generation of the documents. I chose Docusaurus with the Docusarus TypeDoc plugin and automated the documentation generation process to always have it up to date.
  • Mentored and assisted, mostly on Angular, NgRx, RxJS, and unit testing.
  • Designed and led the implementation of fonts APIs—a central repository for managing the font sets and allowing custom fonts to be added for specific customers.
Technologies: Angular, NgRx, RxJS, Unit Testing, Software Architecture

Full-stack Developer

2015 - 2019
  • Founded, developed, and managed an eCommerce platform. It allowed the user to select and customize a gift. The user could select a gift and choose its frame and color, upload a photo from various sources, and send the complete gift by mail.
  • Implemented the front end, which was highly interactive and responsive (mobile and tablet support). It allowed the customers to see the gift in a WYSIWYG way. The frame was presented with the uploaded photo inside.
  • Developed the back end with C#.NET and Web API and the database in MongoDB.
  • Implemented a back-office app where it was possible to modify the product's offer, manage the inventory and orders, or generate reports.
Technologies: C#.NET, ASP.NET MVC, MongoDB, AngularJS, JavaScript, SCSS

Senior Front-end Developer

2017 - 2018
  • Developed a fintech app usage for one of the leading retailers in Poland. The app was an internal tool assisting employees with finance-related topics.
  • Led the platform performance testing process before release and identified the bottlenecks.
  • Gained expertise on handling asynchronicity on the front end as the app was interactive and depended on complex data calculations made by the microservices.
  • Got familiarized with the microservice architecture.
  • Learned about how modern back end and DevOps work. Attended architecture and back-end-related meetings.
Technologies: Angular, RxJS, TypeScript, Microservices

Senior Front-end Developer

2016 - 2017
  • Took part in the rewrite of the eCommerce platform for one of the most recognized retail brands in Poland. The platform was converted into a marketplace where other merchants can add their products and use Empik's well-known and popular brand.
  • Worked closely with the UI/UX department and implemented numerous reusable components used across the platform.
  • Advised on AngularJS-related topics. Provided mentoring to junior developers.
Technologies: AngularJS, SCSS, HTML5, JavaScript, FreeMarker

Full-stack Developer

2013 - 2015
  • Developed a highly available internet booking system for a major European airline.
  • Implemented a complete redesign of the mobile booking system.
  • Worked collaboratively on the new features' architecture.
  • Implemented a set of highly customizable reusable components.
  • Investigated and worked on solving critical production errors.
Technologies: C#.NET, SQL, JavaScript, HTML5, CSS, jQuery, Backbone.js, ASP.NET, ASP.NET MVC

RxJS 7 and Observables | Introduction

Best-selling online video course introducing students to the RxJS library known for its steep learning curve.

RxJS is a trendy library, and there are many videos and courses covering it; however, they appeared to be going too fast as far as the basics are concerned, and a strong understanding of the basics is what is important to use RxJS with success.

My course aims at flattening the learning curve by explaining all concepts one by one. Numerous diagrams and coding sections showcase each feature of RxJS.

The course was curated for the Udemy Business collection.


An eCommerce platform implemented using AngularJS, C#.NET Web API, and MongoDB. It allowed the user to order a gift. A personalized picture frame with their photo inside.

The user could customize the gift in a WYSIWYG way. It was a one-person project, including all the non-technical aspects.

From the technical perspective, it was a great playground to learn new technologies that have helped me implement the front end, back office, back end, database, and run everything on a cloud-based Windows Server.

This project was active in the years 2015-2019 as my side job.

Medium Articles

This is my Medium profile. I have written a few articles related to RxJS, explaining some of its features in detail.

All topics are described in detail and provide the necessary background and playgrounds to test and experiment with the code.


A matchmaking platform for Counter-Strike which was active and first in Poland around ten years ago.

It was based around internet relay chat (IRC) technology. During the peak of this project, there were over 300 games played a day (3,000 players per day).

I co-founded this platform and was responsible for designing, implementing, and maintaining the system. The admins would start new games using a special set of scripts and the players would join those games using the #gather.teams channel on the QuakeNet IRC network.

Everything was handled by a set of bots written in C++ running on a Linux server. For authentication purposes and statistics a MySQL database was used.
2018 - 2020

Master's Degree in Business Administration (MBA)

Kozminski University - Warsaw, Poland

2007 - 2013

Bachelor's Degree in IT Systems Engineering

Warsaw University of Technology - Warsaw, Poland


RxJS, NgRx, jQuery, Backbone.js, Sockets




Angular, ASP.NET, ASP.NET MVC, AngularJS


TypeScript, JavaScript, HTML, CSS, C#.NET, SQL, HTML5, SCSS, C++, PHP


Microservices, Unit Testing


MongoDB, MySQL


Front-end Architecture, Online Tutoring, Software Architecture, IRC

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