Maciej Stempniak

Software Engineer - C++20 and .NET

I shipped 5G RAN control features at Nokia and now build backend services for Poland’s national e-invoicing platform at Symfonia. My C++ simulation engine runs 250-300 games per second and is available as a live WebAssembly demo.

Run C++ demo
Experience
CV

Warsaw, Poland · EU citizenOpen to relocation across the EU

Production experience

Symfonia

.NET Backend Developer

May 2026 - Present

Backend services for Poland’s national e-invoicing platform.

KSeF backend services

Build and debug C#/.NET and GraphQL services for KSeF, Poland’s national e-invoicing platform, using SQL, Hangfire, Dapr, Kubernetes and OPA-based authorization.

API 2.0 migration

Contributed across endpoints, data models, authentication, persistence, GraphQL schemas, Ministry of Finance integration logic and automated tests.

Production investigation

Trace production failures across service layers and build test harnesses, repository documentation and automated validation workflows.

Nokia · 5G RAN

Internship → extended C++ contract after three months

C++ Software EngineerContract · 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 in the team’s production workflow.

What colleagues say

“Maciej demonstrated strong analytical skills as well as wide knowledge of modern C++.”
Krystian PawlakLine Manager at Nokia Mobile Networks

“Very independent developer with no need of supervision, considering his first summer trainee position.”
Kuba ŁukaszczykTechnical Leader at Nokia

View LinkedIn profile

Two-Player Catan Simulation Engine & Game AI

Co-authored with Yaryna Rachkevych BSc thesis University of Wrocław

A C++20 simulation platform for a reproducible two-player Catan variant. It runs seeded tournaments between deterministic heuristics, chance-aware alpha-beta and agents tuned through evolutionary search.

My engineering contribution

Designed the bit-packed board state and fast apply/undo transitions.
Implemented deterministic seeding, replay inspection and multi-agent benchmarks.
Profiled and optimized the engine, then built cross-compiler tests and CI.

59%: Lower per-game cost after profiling and optimization. A representative native Clang 22 -O3 build reaches 250-300 random-vs-random games per second.
<800 B: Fixed board state using bit-packed objects, with fast apply/undo evaluation and no complete-board copies.
3 compilers: 242 generated test cases across six binaries, verified with GCC, MSVC, Clang and AddressSanitizer CI.

Live · C++ via WebAssembly

The thesis engine is compiled to WebAssembly and runs locally in your browser. Choose two agents and run a reproducible tournament.

Browser throughput is device-specific and is not the native release-build benchmark.

Bot AFull handcrafted heuristic strategy.Bot BPrioritises early city upgrades.Games

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

Technical strengths

Production

C++20
C# / .NET
GraphQL
SQL
Dapr
Kubernetes
OPA

Projects & tooling

Python
WebAssembly
Linux
GDB
Valgrind
GoogleTest
xUnit
CI

Languages

Polish · Native

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

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

Concurrent Programming in C++
Algorithms and Data Structures
Computer Architecture

Selected achievements

Academic distinction

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.

Programming competition

Honorable Mention - First Stage, 29th Polish Olympiad in Informatics

Recognised in the first stage of Poland’s national informatics competition.

Additional training

10xDevs 3.0 · 2026

Practical programme covering agent-assisted software development, testing and workflow automation.

Teaching & leadership

Paid one-to-one tutoring · Since 2020

Mathematics & Computer Science Tutor

Since 2020, I have worked one-to-one with more than 20 students, teaching mathematics and computer science and preparing secondary-school students for Polish Matura examinations.

Certified by the Polish Yachting Association · 2023-2025

Sailing Instructor

Over three summer seasons, I taught adults and young people and prepared participants for Poland’s yacht-sailing licence examination.

Open to backend and systems opportunities

I'm interested in roles involving C++, .NET or performance-sensitive backend services, in Warsaw or elsewhere in the EU.

maciek.m.stempniak@gmail.com

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