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.

Навыки

• C#
• .NET 6
• Microsoft SQL Server
• ASP.NET MVC
• Web API
• JavaScript
• HTML
• CSS
• React
• Angular
• Git
• Object-Oriented Programming
• Software Design Patterns
• Test Automation
• Unit Testing