Maciej Stempniak

I build backend and systems software across C++, Python and .NET. I have shipped production C++ for 5G RAN, contribute to KSeF backend services, and use Python for simulation tooling, engineering automation and ML research.

Production C++ · Python Engineering · C#/.NET Backend

Warsaw, Poland · EU citizenOpen to relocation across the EU

Experience

Production experience

Symfonia

.NET Backend Developer

May 2026 — Present

Backend services

Develop and debug C#/.NET and GraphQL services using SQL, Hangfire, Dapr, Kubernetes and OPA-based authorization.

KSeF migration

Contributed to the KSeF API 1.0-to-2.0 migration across endpoints, data models, authentication, persistence, GraphQL and automated tests.

Production and tooling

Investigate production failures and created repository documentation, validation harnesses and a Graphify knowledge graph used by the team with Claude.

Nokia · 5G RAN

C++ Software EngineeringContract · October 2025–April 2026

C++ Summer TraineeInternship · July 2025–October 2025

5G control logic

Developed C++20 logic for temperature-aware cell activation, traffic management and energy management in 5G base stations.

Massive MIMO

Extended operator-configuration handling for Massive MIMO and beamforming functionality.

Verification

Added automated tests, validated changes in simulation, and debugged with GDB and Valgrind before being selected to continue after the internship.

View full experience timeline

Recommendations

What colleagues say

“Maciej demonstrated strong analytical skills as well as wide knowledge of modern C++.”

“Very independent developer with no need of supervision, considering his first summer trainee position.”

View LinkedIn profile

Python engineering

Bot Arena replay interface showing the move log, game state, bot statistics and playback controls.

Tournament infrastructure · Co-developed project

Bot Arena

A Python environment for running programming-game tournaments, enforcing execution limits and replaying completed matches for inspection.

  • Co-developed the project and personally implemented its game logic, map generation, bot interface and package, and timeout enforcement.
  • Built structured match logs and move-by-move replay so bot behavior and game outcomes could be inspected after execution.
  • Python
  • Process management
  • Timeout enforcement
  • Logging and replay
Repository

Toolkit

Technical strengths

Core

  • C++20
  • Python
  • C# / .NET

Backend

  • GraphQL
  • REST APIs
  • SQL
  • Hangfire
  • Dapr
  • OPA

Systems and tooling

  • Concurrency
  • Subprocess management
  • Linux
  • GDB
  • Valgrind
  • Git
  • Gerrit

Testing and delivery

  • Automated testing
  • GoogleTest
  • xUnit
  • CI
  • Docker
  • Kubernetes

AI / ML

  • PyTorch
  • YOLOv8
  • Game AI
Languages

Polish · Native

English · Cambridge C1 Advanced, Grade B · 198/210

Education

BSc in Computer Science

University of Wrocław · 2022–2026

Thesis: Implementation of the Catan board game and AI agents for one-versus-one gameplay. Defended in March 2026.

Selected coursework

  • Advanced C++ and STL
  • Concurrent Programming in C++
  • Algorithms and Data Structures
  • Computer Architecture
  • Advanced Python
  • Machine Learning

Recognition

Selected achievements

Rector’s Scholarship for Academic Achievement · 2023/24

Awarded for academic results achieved in 2022/23. GPA 4.74/5.00; ranked 11th of 160 in the first-cycle Computer Science scholarship ranking.

Teaching & leadership

Clear technical communication

Paid one-to-one tutoring · Since 2020

Mathematics & Computer Science Tutor

Taught mathematics during the first two years and mathematics and computer science from 2022 onward, working with more than 20 students in total and preparing secondary-school students for Polish Matura examinations.

Certified by the Polish Yachting Association · 2023–2025

Sailing Instructor

Taught adults and young people over three summer seasons, preparing participants for Poland’s yacht-sailing licence examination.

About

How I work

I moved into a production .NET role and quickly began contributing to backend APIs, KSeF integration and production debugging. I value C++ for low-level control and performance, and Python for engineering tools, simulation and ML experimentation. My AI-assisted workflow uses explicit plans, controlled repository context, testing and verification.

Contact

Hiring for a technically demanding software role?

I'm interested in backend, systems and applied-ML roles where performance, reliability or correctness are first-class constraints.

maciek.m.stempniak@gmail.com
Email MaciejLinkedInGitHub