Jakub Kubík
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Senior Software Engineer · Invasys

Jakub Kubík

I build reliable Python backend systems with a focus on security – as part of your team or on a project with a clear scope.

How I can help

Get in touchCV
backend experience
7+ years
at Invasys, since 2024
2 years 10 months
at Kiwi.com, 2019 – 2023
4 years 9 months
MSc · LNCS 16231
Springer · research paper

Experience

Experience and education

7+ years of Python backend work – data systems at Kiwi.com, now cybersecurity software at Invasys.

  1. 01/2024 – present2 yrs 10 mosongoing

    Invasys

    1. Software Engineer
    2. Senior Software Engineer

    Brno, Czech Republic

    • Design and build backend services for advanced cybersecurity software used in real-world operations.
    • Work on the data layer and database migrations, containerised services and deployment through CI/CD.

  2. 04/2019 – 12/20234 yrs 9 mos

    Kiwi.com

    1. Junior Software Engineer
    2. Software Engineer

    Brno, Czech Republic · alongside university until mid-2023

    • Built systems that retrieved data from many external sources, using web scraping to keep the data coming in reliably.
    • Built large-scale monitoring pipelines for a high-traffic environment.

  3. 2016 – 2023

    • MSc (Ing.) in Cybersecurity

      Brno University of Technology · 2020 – 2023

    • BSc (Bc.) in Information Technology

      Brno University of Technology · 2016 – 2020

    Publication

    Selfish Mining in Multi-attacker Scenarios: An Empirical Evaluation of Nakamoto, Fruitchain, and Strongchain

    Perešíni, Hladký, Kubík, Homoliak · LNCS 16231, 328–343 · Springer 2026

    Paper (Springer LNCS) Full text (arXiv)

    Master’s thesis smasf framework Bachelor’s thesis Archived Chrome Web Store listing (2025)

Technologies

Backend
  • Python
  • asyncio
  • FastAPI
  • REST APIs
  • SQLAlchemy
Security
  • secure software development
  • network security
  • TLS / PKI
  • WAF
  • CSP
AI-assisted development
  • Claude Code
  • specs and architecture
  • review of every change
  • tests and CI gates before deploy

Full CV

Projects

Selected projects

Research, university projects, a hobby project and a website for a non-profit. Links go to the source code, the publication or the live site.

P-01 · research2023–2026

Selfish mining in blockchains

The simulation framework from my master’s thesis compares how the Nakamoto, Subchain and Strongchain protocols resist selfish miners. The paper in Springer LNCS 16231 (CBT workshop at ESORICS 2025) builds on it and evaluates Nakamoto, Fruitchain and Strongchain with multiple attackers.

  • Single- and multi-attacker scenarios
  • Open source in Python on GitHub (smasf)
  • Python
  • simulations

Paper (Springer LNCS) Full text on arXiv smasf on GitHub

Diagram: an attacker’s private branch grows next to the public chain of blocks.public chainattacker’s private branch

P-03 · hobby project2025 – present

Homelab

My own server where I practise running services the way it’s done at work: isolated services, monitoring, tested backups and documentation.

ozjuliana.sk home page on desktop

P-04 · website2026

ozjuliana.sk

New website · design, development, operations

A website for a small non-profit that collects goods for people in need all year round – fast on mobile, with a simple news admin and no WordPress.

People from the non-profit post collection updates themselves, mostly from their phones.

47.4 kB

Home page HTML and CSS. Half of all mobile sites ship more than that in CSS alone (77 kB, HTTP Archive 9/2026).

Home page size after each change, April–October 2026 (38 versions).

  • Framework-free PHP, articles as JSON files, no database
  • Admin login with a password and Google Authenticator (TOTP in plain PHP)
  • Accessibility: 0 axe findings (WCAG 2 A/AA) in 30 runs over 10 pages
  • PHP
  • HTML
  • CSS
  • JavaScript
  • Apache

Live site : ozjuliana.skCase study : ozjuliana.sk

All projects

Personal

About me

Jakub Kubík

Outside work I go running and look after my own homelab. I also volunteer as the webmaster for a non-profit that helps people in need.

I develop with Claude Code and AI agents. I set the spec, architecture and tests myself and review every change before it ships. AI speeds up my work; I stay accountable for the quality and security of the result.

location
Brno, Czech Republic
education
MSc (Ing.) in cybersecurity, Brno University of Technology
languages
Slovak, English, German (basic)
interests
running, self-hosting and homelab

Contact

Let’s build something together.

Looking for someone to join your team, planning a project, or simply have a question? A few lines by email are enough.

Email me

or write directly to jakupkubik@gmail.com

I usually reply within two working days.

Profiles and CV