Ondrej Beluský, Developer in Brno, South Moravian Region, Czech Republic
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Ondrej Beluský

Verified Expert  in Engineering

Full-stack Developer

Brno, South Moravian Region, Czech Republic
Toptal Member Since
July 30, 2019

Ondrej has over a decade of professional software development experience. He has worked for multinational companies, including Amazon and NetSuite | Oracle. Ondrej is a productive, open-minded developer who can connect the dots, learn new things, and deliver with ease and exceptional quality. He is always optimistic and enjoys mentoring and inspiring people.


Oracle NetSuites
Bash, Jira, Perforce, Oracle Database, JavaScript, Gradle, Kotlin, Java
Bash, Jira, Git, Oracle Database, jQuery, Hibernate, Spring, Apache Wicket, Java
AccuRev, Visual Studio, JavaScript, Microsoft SQL Server, Visual Basic, C#




Preferred Environment

Git, IntelliJ IDEA, Ubuntu

The most amazing...

...project I've worked on was implementing and supporting custom segments across NetSuite, including system-generated transactions.

Work Experience

Principal Software Engineer

2014 - 2019
Oracle NetSuites
  • Implemented custom segments in an ERP module to extend the segmentation capabilities of the system.
  • Implemented support for custom segments across all areas including many system-generated transactions.
  • Reworked and polished legacy custom transactions to be production-ready and fully supported by the plugin framework.
  • Joined modularization group to help modularize legacy code.
  • Developed a tool for analyzing and identifying invalid dependencies of legacy code.
  • Joined the database group to gain more insight about common migrate and performance-related problems, and become the go-to person in our group for reviewing migrates.
  • Applied the principles of React and Redux to drive the adoption of a new NetSuite UI framework.
  • Implemented a new feature based solely on the new UI framework, and communicated with REST services.
  • Mentored newcomers, helped them set up the environment, and ramp them up.
  • Conducted interviews of new developer candidates.
Technologies: Bash, Jira, Perforce, Oracle Database, JavaScript, Gradle, Kotlin, Java

Software Development Engineer II

2012 - 2014
  • Developed an internal system for managing the vendors' chargebacks, waiver rules, notifications, and managing dispute workflows.
  • Implemented new features using the Spring framework, Hibernate, and the Wicket framework using Scrum methodology.
  • Used JDBC template for doing more complex queries as Hibernate proved to be good for CRUD.
  • Wrote unit and integration tests to ensure new features did not break existing functionality.
  • Implemented several Cron tasks for sending email notifications, proactive error detection, and detecting and resolving stale workflows.
  • Participated in technical and API design. My responsibilities ranged from taking requirements, working on the implementation, running tests, and releasing it to production.
Technologies: Bash, Jira, Git, Oracle Database, jQuery, Hibernate, Spring, Apache Wicket, Java

Software Developer

2011 - 2012
  • Developed a new implementation for a large London-based asset manager which culminated in the successful migration of 1.1 billion GBP in assets.
  • Implemented a feature for supporting fixed-term deposits as a new asset type.
  • Built new features with TDD, covering the legacy code with tests to avoid breaking the code.
  • Mentored newcomers to bring them up-to-speed quickly.
Technologies: AccuRev, Visual Studio, JavaScript, Microsoft SQL Server, Visual Basic, C#

Software Developer

2008 - 2010
  • Developed a Planning Wizard platform for quality demand forecasting, efficient material flow, and inventory management.
  • Implemented new features, and fixed incoming issues from customers.
  • Met with customers, analyzed their data and requirements.
  • Improved the process for importing and transforming customer data to the Planning Wizard database.
  • Implemented a sync script for the deploying of a new instance on another server to run parallel computations.
  • Wrote a script for creating SQL diff script from a selected DB instance and reference DB.
  • Worked with different methods for forecasting sales from the historical data.
  • Created a report for a quick overview of the products, their orders, forecasts, inventory and orders in transit.
Technologies: Bash, Subversion (SVN), jQuery, MySQL, Nette, PHP

Visual Simulator and Debugger of Neural Networks

As a bachelor's project, I created a visual simulator and debugger of neural networks. The application has an Edit mode, where you can design and connect the layers. The Next mode is a simulation, which can be run or executed step-by-step, visualizing how the weights are changed.

Prediction of Time Series Using Statistical Methods

I created a library for forecasting a time series as my Master's project. Forecasts are based directly or indirectly on the information derived from historical data. This data may include different patterns such as trend, horizontal, and cyclical or seasonal patterns. Most methods are based on the recognition of these patterns, their projection into the future, and thus, a forecast is created. I used statistical methods as well as neural networks for creating the forecast. I also used a combination of those methods and evolution algorithms to determine the final decision.

Custom Segments in NetSuite

I was part of the core team working on this feature. I also developed tools for easier and unified manipulation of the segments to be used by other developers.

Python Connector for KeePassXC

KeePassXC is a password manager application. It uses a secure protocol for communicating with the browser extension to provide the username and password for a particular website. For many Python scripts, I needed a password and token to log in to a particular service which I did not want to expose in plaintext. I wrote a Python script which would associate and connect to the running KeePassXC instance.
When the Python script needed a password, it would get it from the KeePassXC.

Options and Stock Portfolio Manager

The application connects to the broker via an API, fetches current positions, and stores it in the database. Break-even points, dividend yields, P/Ls, and estimated earnings dates are then computed from the data. It also obtains earnings dates (from multiple sources), ex-dividend and payment dates, and provides a projection for future dividend dates.
All positions and related data are then stored in a Google sheet, which is used as the main UI. I coded it in Python and used MongoDB as the database.
2008 - 2011

Master's Degree in Intelligent Systems

Brno University of Technology - Brno, Czech Republic

2005 - 2008

Bachelor's Degree in Information Technology

Brno University of Technology - Brno, Czech Republic


React, jQuery, NgRx


IntelliJ IDEA, Terraform, Helm, Git, Subversion (SVN), Visual Studio, AccuRev, Jira, Gradle, Perforce, Docker Compose


JavaScript, Java, Go, Python, SQL, Kotlin, PHP, Bash, Visual Basic, C#


Redux, Angular, Nette, Apache Wicket, Spring, Spring Boot, Hibernate


JSON, MySQL, MongoDB, Oracle DBA, NoSQL, Microsoft SQL Server, PostgreSQL


Test-driven Development (TDD), Agile Software Development, Clean Code, Domain-driven Development, REST, Scrum, Kanban


Linux, Ubuntu, DotCMS, Oracle Database, Kubernetes, Amazon Web Services (AWS), Android, Docker


Machine Learning, Neural Networks, Genetic Algorithms, Evolutionary Algorithms

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