Senior .NET WinForms Developer

For our client – an international technology company building high-performance trading systems used by professional market participants – we are looking for a Senior .NET WinForms Developer to join the frontend engineering team responsible for real-time desktop applications. This role focuses on building fast, responsive, custom-rendered desktop UI components. It is not about configuring ready-made UI libraries, but about creating efficient solutions from the ground up. Key responsibilities • Design, implement and optimize custom WinForms controls (charts, grids, interactive visualization components) • Build and maintain high-performance desktop applications handling continuous real-time data streams • Ensure smooth multi-threaded UI updates without blocking or freezing the interface • Collaborate with backend engineers (C++ systems) to maintain low-latency TCP/socket communication • Profile, debug and optimize rendering performance (GC pressure, paint cost, batching, flicker control) • Contribute to improving engineering standards, UI architecture, and usability Ideal candidate profile • 5+ years of experience developing desktop applications in C#/.NET (preferably .NET 8) • Strong hands-on experience with Windows Forms • Proven experience building custom UI controls from scratch (custom rendering, inheriting from base controls – not only configuring UI libraries like DevExpress/Telerik/Infragistics) • Experience working with continuous real-time data streams pushed directly to the UI • Strong understanding of multi-threaded UI applications and safe UI updates from worker threads • Practical experience in UI performance optimization (minimizing redraw cost, GC pressure, flicker prevention, batching updates) • Experience working with TCP / socket-based communication • Ability to explain previous technical decisions and UI trade-offs • English level: min. B2+ Nice to have • Experience with trading systems or real-time financial applications • Familiarity with C++ or C# interoperability with native components • Understanding of high-performance data visualization patterns Conditions • Work model: Remote • Contract type: B2B • Rate: 125–140 PLN/h + VAT Recruitment steps • Phone call with Recruiter • Technical interview with Client (may required 2 rounds) • Feedback and decision W KUBO naprawdę zależy nam na ludziach. Zapraszamy osoby w różnym wieku, o różnych tożsamościach i sposobach funkcjonowania oraz niezależnie od sytuacji zdrowotnej i rodzinnej. Autentyczność jest dla nas wartością, a naszym celem jest uczciwy i otwarty proces dla wszystkich. At KUBO, we genuinely care about people. We welcome candidates of all ages, backgrounds, identities, family constellations, health situations, and ways of thinking and interacting with the world. You’re welcome to be yourself — we value authenticity, and we’re committed to creating a fair and inclusive process for everyone.