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Jan Kowalski

@jankowalski1

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Senior software engineer building reliable C#/.NET desktop and real-time backend systems end-to-end.

Spain

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What I'm looking for

I’m looking for a team where I can own C#/.NET features end-to-end—building reliable real-time systems and desktop experiences, with emphasis on performance, concurrency, and production-grade reliability in high-availability environments.

I’m a Senior Software Engineer with 10+ years building C#/.NET desktop and backend systems across financial services, travel technology, logistics, and public sector domains. I focus on performance, concurrency, and reliability in distributed environments, and I’m comfortable owning features end-to-end—from design through deployment and production debugging.

At Goldman Sachs, I built the GS Real-Time Risk & Market Data Workstation using WPF and MAUI components, integrating backend services and WebSocket feeds to deliver live dashboards. I implemented asynchronous WebSocket ingestion that improved market data processing throughput and reduced message handling latency by 22%, and I reduced failed reconnect attempts by 18% using exponential backoff and circuit-breaker patterns. Previously at Amadeus and LBC Express, I improved API response reliability by 20%, optimized SQL Server queries for latency reduction, and delivered backend services for booking synchronization and parcel tracking—always with a strong emphasis on stability and operational excellence.

Experience

Work history, roles, and key accomplishments

Senior Software Engineer

Goldman Sachs

Oct 2023 - Mar 2026 (2 years 5 months)

Built a .NET desktop risk and market data workstation with WPF/MAUI and WebSocket feeds, improving real-time market data throughput and reducing message handling latency by 22%. Reduced failed WebSocket reconnect attempts by 18% using exponential backoff and circuit-breaker retry logic, and improved production stability by investigating memory leaks and threading deadlocks.

C++.NET WPF .NET MAUI WebSockets Exponential Backoff & Circuit Breakers CI CD Pipelines

Software Engineer

Amadeus

Jul 2018 - Aug 2023 (5 years 1 month)

Contributed to a travel booking partner integration platform by building .NET backend components and WPF desktop tools for reservation synchronization, refunds, and itinerary changes. Improved API response reliability by 20% by refactoring async request handling and adding structured retry policies for external airline systems, and reduced SQL Server query latency by optimizing indexes and removin

C++.NET WPF SOAP REST APIs SQL Server Retry SQL Query Optimization

Software Engineer

LBC Express, Inc.

Nov 2015 - May 2018 (2 years 6 months)

Developed backend services for parcel tracking and logistics management, supporting real-time shipment updates across distribution centers. Integrated third-party courier APIs to synchronize shipment status and automate notifications, optimizing SQL queries to reduce peak-period response times and improve system throughput.

C++.NET SQL Query Optimization API Integration Performance Tuning

Junior Software Developer

Tyler Technologies

Jun 2014 - Oct 2015 (1 year 4 months)

Assisted with development of municipal case management systems by working on backend APIs and UI components for public-sector records management and reporting workflows. Fixed bugs and implemented small ASP.NET features, supporting regression testing and release validation across multiple departments to improve stability and user experience.

C++ASP.NET Backend UI Components Regression Testing