Ondrej Hirjak, Developer in Bratislava, Bratislava Region, Slovakia
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Ondrej Hirjak

Verified Expert  in Engineering

Software Engineer and Developer

Location
Bratislava, Bratislava Region, Slovakia
Toptal Member Since
February 5, 2019

Ondrej is a software architect with technical management skills and 19+ years of experience in shipping projects, from low-level kernel drivers and GPU computations to high-speed peer-to-peer networks and enterprise finance and gaming apps. He has hands-on experience in the software development lifecycle, from ideas to live operations, focusing on high-level architecture, design, and management. Ondrej thrives on projects where he takes ownership and delivers the project from start to finish.

Portfolio

Wincent
FIX Protocol, Rust, Kotlin, Amazon Web Services (AWS), Trading, Python...
Blockchain projects
TypeScript, Cardano, Decentralized Exchanges (DEXs), Blockchain...
Freelance Clients
Kotlin, Figma, Full-stack Development, APIs, Front-end, Database Modeling...

Experience

Availability

Full-time

Preferred Environment

Linux, MacOS

The most amazing...

...project I've worked on is a complex casino system serving hundreds of thousands players around the globe and running on thousands of machines.

Work Experience

Senior Software Engineer

2022 - 2023
Wincent
  • Developed an OTC platform for a major crypto market maker.
  • Engaged in communication between teams to enable future extensions of the platform.
Technologies: FIX Protocol, Rust, Kotlin, Amazon Web Services (AWS), Trading, Python, Cryptocurrency, Trading Systems, Kubernetes, Apache Kafka, Back-end, SQL, Docker, NoSQL, Asynchronous Programming, WebSockets, REST APIs, Crypto, JSON, QuickFIX, Monorepos, Redis, Message Queues, Databases, Algorithmic Trading, API Design

Head of Development

2022 - 2022
Blockchain projects
  • Oversaw product and software development of DEX on Cardano.
  • Managed three software engineering teams, each of around five people.
  • Provided product guidance, marketing, and top management support.
Technologies: TypeScript, Cardano, Decentralized Exchanges (DEXs), Blockchain, Team Leadership, Technical Leadership, CTO, Amazon Web Services (AWS), JavaScript, Cryptocurrency, Node.js, React, Leadership, Full-stack Development, Asynchronous Programming, Front-end, Non-fungible Tokens (NFT), Full-stack, Crypto, JSON

Senior Software Engineer | Architect | Consultant

2019 - 2022
Freelance Clients
  • Oversaw the project management of the AICO Olympic Pins Catalogue app (https://aicolympic.org/aopc-app).
  • Built the server architecture and oversaw Kotlin development and Azure cloud infrastructure (https://aipowered.city).
  • Performed Envision platforms integration with C#, Java, and AutoHotkey, (https://brain.industries/envision).
  • Embedded device power consumption optimization (https://telematix.compexinc.com); Made DevOps process improvements in Tatra banks (https://www.tatrabanka.sk).
Technologies: Kotlin, Figma, Full-stack Development, APIs, Front-end, Database Modeling, REST APIs, Spring Boot, Full-stack, CSS, HTML, Continuous Integration (CI), JSON, Embedded Development, Redis, Message Queues, Databases, Twilio, Windows API, Win32 API, Windows App Development, API Design

Software Architect | Senior Software Engineer | IT Consultant

2012 - 2018
Vnet-Services GesmbH
  • Implemented the player-management-and-tracking module of a casino management system.
  • Designed, implemented, and operated a jackpot module for a casino management system.
  • Installed a new communication layer between the slot machines and casino system.
  • Consulted, developed and supported deployment and operation of a casino management system in many countries for many customers.
  • Co-designed homegrown tools for deployment and configuration management.
  • Led the development of a new ATM-like machine for a casino environment.
  • Managed the development and integration of custom HW modules in a casino environment.
  • Analyzed and prototyped new features and integrations for a casino management system.
Technologies: Ansible, PostgreSQL, Oracle, Protobuf, Qt, C++, Java, Technical Leadership, CI/CD Pipelines, JavaScript, Python, Multithreading, Team Leadership, Back-end, Architecture, SQL, Node.js, Angular, Agile, Leadership, Full-stack Development, APIs, Unit Testing, Front-end, Database Modeling, Networking, REST APIs, Spring Boot, Embedded Software, CSS, HTML, Continuous Integration (CI), Continuous Delivery (CD), Monorepos, Embedded Development, Message Queues, Databases, API Design, Oracle Database

Software Architect

2011 - 2011
Unicorn Systems s.r.o.
  • Defined software architecture and developed internet banking for Tatra Banka.
  • Designed and implemented the graphing component for internet banking.
Technologies: Flash, Flex, Java, Architecture

Senior Software Engineer

2009 - 2011
Tempest a.s.
  • Designed and implemented parts of an enforcement module in an electronic toll collection system in Slovakia.
  • Oversaw the component testing in an electronic toll collection system in Slovakia.
Technologies: Linux, Windows, MySQL, Java

PhD Student, Teaching Assistant

2009 - 2010
Slovak University of Technology, Faculty of Informatics and Information Technologies
  • Worked on a real-time ray-tracer on GPU.
  • Supervised students with their bachelor's theses.
Technologies: NVIDIA CUDA, GPGPU, C++, SQL, Database Modeling

Software Engineer Intern

2008 - 2008
NVIDIA
  • Developed low-level Linux driver for NVIDIA graphics cards.
  • Helped implement cutting-edge features for the Quadro product line.
Technologies: Linux, OpenGL, X11, C, Embedded Software, Monorepos

Software Engineer

2006 - 2008
Tempest a.s.
  • Worked on high-speed peer-to-peer network developed for Cisco.
  • Implemented various low-level modules.
  • Worked on integration layers between high-level components written in Java and low-level components written in C.
Technologies: Linux, C, Java, Networking

Software Engineer

2005 - 2006
Digital Systems s.r.o.
  • Designed and implemented reconciliation software for ING bank.
  • Built a SWIFT system for banking sector.
  • Developed the back-end for T-Com Games T-Station.
Technologies: Linux, C++, Oracle, MySQL, Java, Microsoft SQL Server, ASP.NET, C#, Database Modeling, Databases, Oracle Database

Software Engineer

2004 - 2005
Isotoxin Industries s.r.o.
  • Implemented various games using the Cipher Engine.
  • Created our own Radiant-like game editor.
  • Designed and implemented a parking lot utilization management server.
Technologies: Linux, MySQL, OpenGL, C++, Game Development, Game Engine Programming, Windows API, Win32 API, Windows App Development, API Design

OTC Platform

I did the OTC trading platform design, implementation, and operations. I also did cross-team interactions with stakeholders, traders, counterparties, and DevOps.

Skills: HFT, OTC, Rust, AWS, DevOps, Kotlin, FIX, Python

AICO Olympic Pins Catalogue

https://aicolympic.org/aopc-app
I did the project management of AICO Olympic Pins Catalogue app for both web and mobile.

I oversaw the project, product, and requirements/scope management. I delivered the application on the customer side.

AI-powered City

https://aipowered.city
I designed the server and back-end architecture in the Azure cloud. I also oversaw the deployment and operations of the back-end events processing design.

I developed the server back end in Kotlin and the administration front end in Vue.

CashBox

For CashBox, I led the development of custom ATM-like machine for casinos environment.

WORK DONE
• Analyzed and designed the solution.
• Oversaw the development of the front- and back-end of the server and embedded HW integration part.
• Set up the deployment and supported the operation.

Technologies: Java, Dropwizard, C++, Qt, Protobuf, PostgreSQL, Ansible

Casino Management System

For seven years, I've worked on various parts of a complex casino management system codenamed TBO. The system is successfully serving hundreds of thousands of players around the globe and running on thousands of machines.

WORK DONE
• Implemented player management and tracking module.
• Designed, implemented, and operated a distributed jackpot module.
• Developed a new communication layer between slot machines and casino system.
• Consulted, developed and supported deployment and operation of a casino system for a number of clients all around the world.
• Co-designed homegrown tools for deployment and configuration management.
• Led the development and integration of custom HW embedded modules in a casino environment, most notably the "SAS over IP" custom SMIB (slot machine interface board).
• Analyzed and prototyped new features and integrations of a casino management system.

Technologies: Java, Spring, C++, Qt, Protobuf, Oracle, PostgreSQL, Ansible

Tatra Bank Internet Banking

While working for Unicorn Systems, I developed various parts of internet banking for the Slovakian bank, Tatra Bank. Most notably, I designed and implemented the graph components for the front end.

Technologies: Flex, Flash, Java

ETC EFBO

Worked on Electronic Toll Collection System for Slovak Republic, in particular Enforcement BackOffice System.

Implemented parts in Java, created build system based on Ant, estimated project and modules scope.

Graphics and GPU Programming

https://hirjak.io
During my PhD studies, I implemented a basic real-time raytracing engine. Before that, during my university studies, I implemented real-time fluid simulation on GPU.

Technologies: C++, GPGPU, CUDA

NVIDIA GPU Linux Kernel Driver

While interning at NVIDIA, I developed new features and implemented bugfixes for a low-level Linux driver for their graphics cards.

Technologies: C, X11, OpenGL, Linux

High-speed Peer-to-peer Network

Being a part of an extremely capable team of people, I worked on a high-speed peer-to-peer network developed for Cisco called Topos. I implemented various low-level modules and worked on integration layers between high-level components (written in Java) and low-level components (written in C).

Technologies: Java, C, Linux

Recopay

In the process of migrating from old technologies, I also analyzed an old MS Access-based solution and implemented new reconciliation software for ING bank.

Technologies: C#, ASP.NET, Microsoft SQL

Parking Lot Utilization Management Server

As a part of a complex parking solution for the city of Martin, I designed and developed a parking lot utilization management server.

Technologies: C++, MySQL, Linux

Cipher Engine Games and PhaseONE Level Editor

I've also developed various games based on the Cipher Engine. For level editing, I created my own Radiant-like level editor named PhaseONE.

Technologies: Cipher Engine, C++, OpenGL
2009 - 2010

PhD (Unfinished) Degree in Software Engineering

Slovak University of Technology - Bratislava, Slovakia

2006 - 2008

Master's Degree in Software Engineering

Slovak University of Technology - Bratislava, Slovakia

2002 - 2006

Bachelor's Degree in Software Engineering

Slovak University of Technology - Bratislava, Slovakia

Libraries/APIs

MyBatis, Protobuf, REST APIs, OpenGL, jQuery, Node.js, React, Vue, Windows API, Win32 API

Tools

Git, SourceTree, Jira, Confluence, Subversion (SVN), Apache Maven, Ansible, IntelliJ IDEA, Flash, Perforce, Qt Creator, Figma

Languages

Java, C, C++, SQL, Bash, Python, C#, UML, Kotlin, Rust, JavaScript, Scala, XML, Assembler, TypeScript, CSS, HTML

Paradigms

DevOps, Agile Software Development, Scrum, Kanban, Object-oriented Programming (OOP), Agile, Unit Testing, Continuous Integration (CI), Continuous Delivery (CD), Functional Programming, GPGPU, Management, Asynchronous Programming, Windows App Development

Industry Expertise

Trading Systems

Platforms

Linux, MacOS, Oracle, NVIDIA CUDA, MS-DOS, Windows, Android, Azure, Embedded Linux, Docker, Cardano, Blockchain, Amazon Web Services (AWS), Kubernetes, Apache Kafka, Azure Event Hubs, Twilio, Oracle Database

Storage

Database Modeling, Databases, MySQL, Microsoft SQL Server, PostgreSQL, NoSQL, JSON, Redis

Frameworks

ASP.NET, Flex, Spring, Dropwizard, Qt, .NET, Angular, Spring Boot, Ant Design

Other

Software Engineering, Back-end, Embedded Software, TCP/IP, Analysis, Consulting, Team Leadership, Prototyping, Software Architecture, Software Design, FIX Protocol, Technical Leadership, Trading, Multithreading, Architecture, Leadership, APIs, Algorithmic Trading, API Design, X11, Design, Device Drivers, Integration, Game Development, Game Engine Programming, SOAP, Decentralized Exchanges (DEXs), CTO, CI/CD Pipelines, Cryptocurrency, Full-stack Development, Front-end, Non-fungible Tokens (NFT), WebSockets, Networking, Full-stack, Crypto, QuickFIX, Monorepos, Embedded Development, Message Queues

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