Senior .NET Developer

#vacancy #.NET # C# #job #Poland #Senior #backend #Kraków

📌Twinslash

🚀 We’re Hiring: Senior .NET Developer

🌍 Location: Hybrid — Kraków, Poland

⚠️ We are looking for a Senior .NET Developer to join an international team working on solutions in the Banking and Finance sector. The role focuses on developing scalable, high-performance .NET applications, building reliable backend services, and contributing to modern software architecture and continuous improvement.

🛠 Key Skills

• C# / .NET 6+ • Microsoft SQL Server • ASP.NET MVC & Web API • JavaScript, HTML & CSS • React, Angular or similar modern frameworks • Git • Object-Oriented Programming • Software Design Patterns & Architectural Best Practices • Test Automation & Unit Testing • CI/CD • Scalable Application Design • A/B Testing • Fluent English

📋 Responsibilities

• Translate business requirements and user stories into effective application features • Design, develop, and maintain clean, efficient, reusable, and reliable code using C# and .NET • Develop and maintain backend applications and Web APIs • Build reusable C# components and libraries • Contribute to front-end development using JavaScript, HTML, CSS, and modern frameworks • Ensure high standards of code quality, maintainability, and performance • Optimize applications for scalability, responsiveness, and reliability • Implement automated testing and unit testing practices • Identify, troubleshoot, and resolve defects, bottlenecks, and complex technical issues • Contribute to continuous integration, deployment, and production releases • Participate in the ongoing development and improvement of .NET-based solutions • Apply software design patterns and architectural best practices • Collaborate with the team to deliver robust solutions for business-critical processes

🎯 Requirements

• 5+ years of professional software development experience • Strong commercial experience with C# and the .NET ecosystem • Hands-on experience with .NET 6 or later • Solid experience with Microsoft SQL Server • Good knowledge of ASP.NET MVC and Web API • Experience with JavaScript, HTML, and CSS • Experience with React, Angular, or similar modern front-end frameworks • Strong understanding of Object-Oriented Programming principles • Experience developing reusable C# components and libraries • Knowledge of software design patterns and architectural best practices • Understanding of scalable application design and development principles • Experience with automated testing frameworks and unit testing • Hands-on experience with Git and source control practices • Understanding of CI/CD practices • Experience troubleshooting and optimizing application performance • Ability to work independently on complex technical problems • Full professional proficiency in English

➕ Nice to Have

• Experience with A/B Testing • Experience in Banking and Finance • Experience working with large-scale enterprise applications • Experience with modern front-end frameworks • Experience with continuous integration and deployment tools • Experience working in Agile development teams

📍 Work Format

Hybrid position based in Kraków, Poland.