Bart Kozal
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9+ years of professional experience


UI Engineer · May 2018 - present


Software Developer · May 2017 - May 2018In Catawiki, I was a member of Search & Discovery team. My two main responsibilities were: a technical migration of outdated Rails based infrastructure to modern JavaScript environment and improving existing features like search results, categories, auction list page etc. During my work I have learned a lot about heavily data-driven approach through A/B testing and how to collaborate with over 60+ developers. Our stack included and I worked on daily basis with: Rails, React, Redux, TypeScript, Flow, Webpack, Jest, ES6+ and other, modern front-end technologies.

Shelly Cloud

Co-founder & CEO · Oct 2012 - Apr 2016

Shelly Cloud was an automated hosting platform that made deployment of Ruby applications painless. I was a core team member and then a CEO. We hosted over 270 paying applications on 430 virtual servers. I worked in all areas required to built and run successful PaaS: user experience, front-end and back-end development, servers administration, support, marketing, sales and team management. The stack was including and I had to be familiar with the following technologies: Ruby, Rails, AngularJS, Chef, OpenStack, Ceph, GlusterFS, nginx, Varnish, HAProxy, PostgreSQL, MySQL, Elasticsearch, Redis, Git and more.


Software Developer · Jun 2010 - Apr 2016

I worked as a designer, JavaScript and Ruby consultant for various European startups. Below, I listed projects I was a part of and my main responsibilities:

CertAce · Network for data scientists

I worked on releasing MVP in Rails, PostgreSQL and Vue.js.

Masii · Simplified comparison

I worked on mobile version of existing Ember.js app.

GetSafe · Manage all your insurance policies

I coordinated and implemented major redesign of a mobile app written in Ionic.

Crowdestates · Property investment made simple

I worked on releasing MVP in Rails and PostgreSQL.

Locafox · Offline shopping experience for online and mobile consumers

I worked on a client web app written in AngularJS.

Teon · Free online car manuals

I worked on a migration of existing Sencha app to Rails and MongoDB.

Tutoria · Individual tutoring services for students

I built a spinoff app for online collaborative learning using Rails and websockets.

Side projects

Projects I created and develop in my free time:

Games Tracker · Track your games collection

Single page app built in React and powered by API built in Rails.

Echotags · Hands-free, offline audio guide to Amsterdam

Native iOS app built in Swift using UIKit, Core Location, Core Audio, RealmDB and Mapbox API. Supported by Rails web app to manage content.

Checkers for iMessage · Board game for iOS10 iMessage

Native iOS app built in Swift using SpriteKit. One of the first iMessage apps on the market promoted by Apple with over 150.000 users. There are more details in an interview I gave to Indie Hackers.

Coypu · Text-editor-like weekly planner

Built in Vue.js, Electron and PouchDB.

Jottings · Real-time collaboration in Markdown

Built in Rails, Vue.js, Express and ShareDB. Extensively use Operational Transformations and contenteditable API.

Open source projects

Minor contributions: ycmd, rails and other.

Dribbble shots

Other achievements

I published many technical and non-technical articles at Medium, Ragnarson Blog, SitePoint, gave over 20 talks at various meetups like meet.js, Twente.rb, WRUG, TRUG and finished two 48h hackathons Rails Rumble 2012 and Rails Rumble 2015.

I also started local Ruby User Group and tech/startup community at my home city.