Jozef Vaclavik, Developer in Bratislava, Bratislava Region, Slovakia
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Jozef Vaclavik

Verified Expert  in Engineering

Software Developer

Bratislava, Bratislava Region, Slovakia
Toptal Member Since
October 7, 2014

Jozef loves fighting through complex problems and finding optimized solutions for them. He is an experienced business and project manager and team leader who has worked in administration and security with front-end and back-end software architectures.



Preferred Environment

Docker, Xcode, Atom, Terminal, MacOS

The most amazing...

...thing I've done is to migrate a legacy PHP application with a MySQL database (almost 100 tables) that did not have any description into a new Rails project.

Work Experience

Freelance Developer

2009 - PRESENT
  • Led Ruby on Rails projects.
  • Developed iOS applications.
  • Migrated legacy projects into Rails apps.
  • Performed penetration testing for iOS banking apps.
  • Created automated API communication between a student academic system and government systems.
Technologies: Docker, Linux, Ruby on Rails (RoR)


Information system for IUVENTA (government organization in Slovakia). The system is used by nonprofit organizations and their members who received financial support from IUVENTA. They manage their members, teams, and events organized by their members. The Slovak government uses IUVENTA to financially support nonprofit organizations and Vivant to get data about these organizations.


Information system for IUVENTA (government organization in Slovakia). This system is designed to manage the donation application process for various organizations. IUVENTA uses it further to evaluate these applications and collect additional documents.


Information system developed for Vysoka Skola Manazmentu in Trencin/City University of Seattle in Bratislava. It is a complex academic system for managing students, teachers, courses, payments, and the whole academic infrastructure. It contains almost 100 database tables and uses several channels to export/import data to/from other systems. This system was migrated from a legacy PHP application with no description or documentation.

PhotoCloud App

In 2010, I developed the PhotoCloud App for iOS along with a friend. It was a simple photo frame application that you could use to display your pictures on your iPad/iPhone. The application was designed to work over the cloud to allow multiple users to watch the same album together over the internet (e.g., watching pictures from your graduation with your parents while you are in California and they are in New York). The application was discontinued in 2011.


Trifle is a performance monitoring tool for Ruby on Rails applications. It performs data analysis and learns trends to identify anomalies that should later be analyzed. Trifle is written with a Ruby on Rails back-end and an Ember.js front-end. I started the project in July 2014 as a side project and it has been up and running since April 2015.

Online Debrief System

I worked on an application that displays statistical information about surveys performed in hospitals. The application uses a Rails back-end and Ember.js front-end. My primary responsibility was the front-end, which required lots of charts, interactions, data caching, and tests.

TED-Ed Clubs Analytics

I helped develop an analytics dashboard for TED-Ed Clubs. The back-end is served through Ruby on Rails, and the front-end was built using Ember. My primary responsibility was to build the front-end and help with design requirements for the API endpoint. Lots of charts, caching, and data crunching.

TED-Ed Lessons Editor

I took over development of TED-Ed's lessons editor that is used to create interactive lessons from youtube videos. The user creates additional context, enables questions through the video, and creates discussion threads for the viewer.


As a member of a development team that created an eCommence solution for vendors and suppliers, my responsibilities were to create recurrent orders with automatic schedules and processing and to build up the integration side of the application that allowed users to synchronize products and orders to their Quickbooks Online and Quickbooks Desktop accounts.


As a part of a team working on commerce application, I was responsible for building Rails API endpoints in JSON API format and building the inventory tracking part of the application. We ensured that the application has full test coverage as well.
2012 - 2017

Bachelor's of Science Degree in Information Systems

City University of Seattle - Seattle, WA


Xcode, Terminal, TextMate, Atom


Ember.js, Ruby on Rails (RoR), Phoenix, Cocoa Touch, Cocoa


Ruby, Elixir, Objective-C


MacOS, iOS, CentOS, Docker, Linux


MongoDB, MySQL, Redis, PostgreSQL


Agile Software Development, Pair Programming

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