Jiri Hysek

Full-stack developer

A creative programmer with over 17 years of experience in the commercial sector. Ruby on Rails & React developer, hobby game dev, tech enthusiast, quick learner.

I believe the best solution is often the simplest one.

Ruby on Rails
Javascript / Typescript
Godot Engine

Web App Development

  • Ruby on Rails - I used Ruby on Rails as my main framework for web apps between 2006 and 2020. As a freelancer, I used RoR for countless projects (auctioning systems, CRM, CMS, e-commerce, API servers for mobile apps, social network, medical databases, and backends for React frontends).
  • Test-driven development
    - RSpec, Capybara (RoR),
    - React testing library + Jest (React.js)
  • React.js - I've been using it in full-time job since 2020 to 2023.
  • Next.js - a framework for React.js. I use it for my personal projects like this website, zerovendor.com, dottygames.com, and more.
  • Javascript, Typescript
    - with React and Node.js
  • Node.js, Express, Fastify, NestJS
    - backend services in my full-time job, and for various personal projects.
  • MySQL, PostgreSQL, MongoDB, Firebase
    - MySQL mostly for personal stuff and my own projects
    - PostgreSQL for a product in my full-time job
    - Experiments with NoSQL databases like MongoDB and Firebase, used in some of my hobby projects

Game Development

  • Godot Engine
    • iOS / Android / web / Win / Mac / Linux games
    • I've created about 20 games within game jams. Check them out at jhysek.itch.io, it's fun!
    • Several mobile games for preschool children (see puntici.cz) - A few marketing games during my freelance times

Mobile App Development

I've been creating multiplatform mobile apps using frameworks like Ionic, Phonegap, or Corona SDK. Unfortunately, apps made in those frameworks sucked couldn't compete with native apps. Therefore, I'm not currently making mobile apps, but I'd love to experiment with some fresh frameworks, such as React Native.

Invoice Home Inc.

2023 - now
Ruby on Rails developer for one of the most popular invoicing system in the United States. Full remote.
Ruby on Rails
Unit tests
E2E tests


2018 - 2023
Full-stack senior developer. I worked on various SaaS products such as:
Ruby on Rails
Unit tests
E2E tests

Freelance programmer

2008 - 2018
Web applications, multiplatform mobile applications. I worked for a lot of various clients during those 10 years, from the smallest ones to big pharmaceutical companies.

Selected clients / projects:

  • GSK, Baxter (pharma companies) (2012 - 2014) - web and mobile apps (patient register, interactive materials for company representatives, API servers). Subcontractor for Avantea s.r.o. Ruby on Rails.
  • Madeta a.s. - mobile application; subcontractor for Aspa Mobile s.r.o.
  • Blueberry Apps s.r.o (2014) - worked remotely within the developer team; test-driven development, code reviews; Worked on projects "Mr. Parkit" and "Cashplay", both in Ruby on Rails.
  • Účetnictví online (2010 - 2013) - worked on several internal information systems + auctioning system for an art gallery Arcimboldo. Ruby on Rails, test-driven development.
  • Jamujam.com (2017 - 2020) - a social network and collaborative tool for making music; Ruby on Rails + AngularJS
  • Jdu behat s.r.o. - maintenance of Ruby on Rails web app.
  • TV Region s.r.o. - mobile guides for tourists for several South Moravian regions.
  • Microregion Nový Dvůr - several simple Windows games used on a flat touch screen in a tourist info center of the microregion.
  • Transport research centre (2013) - public research institution; worked on internal information system; test-driven development, Ruby on Rails API server, AngularJS frontend
  • Research Partners s.r.o (2014 - 2015) - clinical research organization; test-driven development of two internal systems used in hospitals for storing data about the treatment progress of specific disease; Ruby on Rails
  • Aspa Mobile (2015) - worked as a subcontractor on several mobile applications.
  • TANK s.r.o. / Mercuria Finance (2010 - 2014)
    - Online app for comparison of financial products (Python + Django)
    - API for using results on different websites (Ruby on Rails)
  • Quantum a.s. (2010)
    - Intranet solution - Subcontract for Shean s.r.o.
    - Ruby on Rails
  • Internetovy-prodej.cz (2009 - 2010) - administration part of the e-commerce platform used by their clients; PHP
  • ... and a lot of smaller clients
Ruby on Rails

APCentrum.cz - auctioning & e-sourcing system

2006 - 2011
Programming an e-sourcing & auction system. Started during my studies, and continued as a freelancer in 2008.
Ruby on Rails


2007 - 2008
A couple of smaller projects - an unix daemon for scraping SEO-related data (Haskell); an app for configuration and pricing fences (PHP)

EuroScreen - advertisement panels

2004 - 2005
Software for advertisement panels; work during my studies.

My projects

I created a few own projects. Unfortunately, most of them rest in peace already. Still, the experience is priceless.

Zero Vendor

2021 - now
Work in progress, a catalog of supplier profiles, and vending platform (in progress). An evolution of CoVpoint - quickly created and delivered system for managing demands and offers during Covid times, used by the goverment of the Czech republic for free.
Co-founder, Programmer
Ruby on Rails

Crypto Heroez

Apr 2021 - now
My pre-smartcontract Cardano NFT project was made to learn about the technology. Everything was made from scratch by myself (code, minting, art, website). One of OGs of Cardano NFTs.
Founder, Programmer, Artist


Oct 2021 - now
On-chain procedurally generated NFTs. Everything was made from scratch by myself (code, minting, art, website). Made to explore the ability to store a complete image generator into the blockchain without using external storage like IPFS.
Founder, Programmer, Artist

Applicastore.com - e-commerce system

2014 - 2022
Modular e-commerce solution, in-place editing of texts, easy-to-use solution.
Co-founder, Programmer
Ruby on Rails


2010 - 2022
An auctioning & e-sourcing system. We had several clients. It was lso used as a white-label solution.
Founder, Programmer
Ruby on Rails


2010 - 2012
CMS SaaS for easy in-place editing of websites for small companies and freelancers. Easy to use even for non-technical people. A few websites made with it run till now.
Founder, Programmer
Ruby on Rails


2009 - 2011
Easy to use CMS focused on making microsites with a couple of useful functions like semi-automatic catalog registration or page rank info (back in the time it was actually useful). Even one of the top Czech IT portals noticed it - see the article (in Czech)
Founder, Programmer
Ruby on Rails

Linux security - Talks & Papers

  • Intruder in the Linux system - a talk at a security conference, Hotel Olympik, Praha, 14.9. - 15.9. 2004.
  • Presence hiding techniques in Linux systems - a talk at UNIX/Linux security conference, Hotel Olympik, Praha (see the review on root.cz), 22.6. - 23.6. 2004.
  • Linux rootkit - four articles for Hakin9 magazine, 2004.
  • Rootkits based on VFS hooking - an article for Prielom #24 @ hysteria.sk, 28.3. 2006
  • Kernel rootkits detection - an article for Prielom #22 @ hysteria.sk, 28.2. 2004

Formal Verification - Talks & Papers

I have published a couple of articles on formal verification that were presented at research conferences during my unfinished Ph.D. studies.

  • Model-Based Design and Verification of Reactive Systems - a talk at EUROCAST 2009 in Las Palmas de Gran Canaria + article in Lecture Notes in Computer Science 2009
  • Visual design of SmallDEVS models using statecharts. - presentation at ASIS 2008 conference
  • Evoluční návrh s využitím přepisovacích systémů. - presentation at EEICT 2007 conference
  • Game Jams
    Game jam is an event where participants make a video game from scratch in 48h. Check out my games at jhysek.itch.io. I made like 20 of those.
  • Educational mobile games for children
    Games for preschool kids, mainly in Czech but one of the games is localized also to English and Spanish.

    I started it with my daughter because I wanted to spend some fun time with her but I don't like playing with dolls. So we made a game! She was doing voiceovers when she was 4 years.

    - Puntici.cz (czech)
    - DottyGames.com - not really ready yet
  • Cardano
    This technology is just fascinating. I wanted to learn it so I created a vending machine for on-the-fly generating and selling NFTs. I even took a Plutus pioneer program organized by IOHK to learn to write smart contracts in Haskell.
  • Programming languages

    It's always fun to learn a new interesting programming languages! I worked with a lot of them in the past. The next languages I'd love to have time to learn are Rust, Go, or Elixir. So if you have a project I could learn those on, let me know ;)

I suppose, someone would like to learn about my education. So here you are:

Brno University of Technology

Unfinished Ph.D. degree

2007 - 2011
Thesis area: Formal verification, Title: Formal Verification of Systems Specified by High Level Visual Languages. Published a couple of papers, see the 'Talks' section.
Formal Verification

Master Degree

2005 - 2007
Thesis area: Artificial intelligence, Title: Evolutionary Design Using Rewriting Systems
Evolutionary Algorithms

Bachelor Degree

2002 - 2005
Thesis area: Computer security, Title: Security of UNIX Systems at the Kernel Level