We are looking for an experienced .NET WinForms Developer to join the frontend engineering team and help build high-performance, real-time trading applications used by professional traders. This role is not about configuring UI frameworks - it is about crafting fast, responsive, custom-rendered desktop UI. IN SHORT:🌎 100% remote or from the office (Wrocław, Bielsko-Biała) - You choose!💰 125 - 140 PLN/h☑️ B2B contract💻 >5 years of commercial programming experienceYour Daily Missions Design, implement and optimize custom WinForms controls (charts, grids, interactive visualization components). Work with continuous real-time data streams and ensure ultra-responsive UI under load. Ensure smooth multi-threaded UI updates without blocking or freezing. Collaborate with backend engineers (C++ systems) to maintain low-latency TCP/socket communication. Profile, debug, and tune rendering performance (GC pressure, paint cost, batching, flicker control). Improve engineering practices, and influence UI architecture and usability.  The Essentials We're Seeking 5+ years of hands-on experience developing desktop applications in C#/.NET (preferably .NET 8). Strong expertise in Windows Forms. Proven experience building custom UI controls from scratch (inheriting from base controls and implementing custom rendering - not configuring DevExpress/Telerik/Infragistics). Experience working with continuous real-time data streams, where data is pushed to the UI (not periodic refresh). Strong understanding of multi-threaded UI applications (updating UI safely from worker threads, avoiding freezes and stalls). Practical experience in UI performance optimization (reducing redraw cost, minimizing GC pressure, batching updates, preventing flicker). Experience working with TCP / socket-based communication. Ability to clearly explain previous UI design decisions, trade-offs, and the impact on end users. Fluency in English (minimum B2+).  Nice to Have Experience with trading systems, market data, or real-time financial applications. Familiarity with C++ or interoperability between C# and native components. Understanding of high-performance visualization and data interaction patterns. Reasons Why You Would Enjoy Working With Us We work in the latest technologies and with international clients, and our projects are polished from < to /> - learn about some of the projects we have completed. We organize TechTalks, meet-ups and create guilds where we exchange knowledge - you can learn a lot from your teammates. We have a close-knit team and we make sure to have regular integrations - we often go out to celebrate together. You can work remotely or choose to work from our offices in Wroclaw or Bielsko-Biala. However, we count on your openness to occasionally visit the office for team meetings or client visits, or possible occasional trips to the client's headquarters. You can adjust your working hours to suit your needs, starting your day between 7:00 and 10:00 am. You can work with great specialists in their fields who also have a sense of humor and other after-hours hobbies. It is the people who create the unique atmosphere and relaxed atmosphere at CSHARK. We have a flat structure - we are not a corporation and don't want to be one 🙃. We offer bonuses for employee referrals (from 3000 PLN to 7000 PLN). We organize remote English classes and provide access to the company library. You can also become an author/author of articles published on our technical blog - https://cshark.com/blog/.