Senior .NET Engineer: Legacy-to-.NET 8 Migration Lead

Reply Polska Sp. z o.o.; Katowice; Hybrid; PLN 180,000 - 240,000; Full time

Job summary

Nexi Digital is seeking a Senior Software Engineer to drive the modernization of a payment platform by migrating a large ASP.NET WebForms/MVC monolith from .NET Framework 4.x to .NET 8, updating the data layer and integrations in an on-premise environment.

You will apply SOLID and clean-architecture principles, mentor the team, and leverage AI-assisted tools to accelerate analysis, refactoring and test generation in a hybrid work setup.

Qualifications

• University degree in computer science or comparable field.
• 6+ years of commercial software development experience.
• Experience with C# and .NET across generations (Framework 4.x to .NET 8).
• Experience with migrating legacy applications (re-platforming, incremental refactoring).
• Knowledge of SOLID principles and clean architecture.
• Experience with SQL Server and data-layer refactoring.
• Experience with AI-assisted development tools (e.g., GitHub Copilot).
• Experience with automated unit and integration testing.
• Fluency in Polish and good English communication.

Responsibilities

• Migrate a large ASP.NET WebForms/MVC monolith from .NET Framework 4.x to .NET 8.
• Refactor to SOLID and clean architecture within the migration scope.
• Modernize SQL Server data layer and system integrations.
• Leverage AI-assisted tools to accelerate analysis, refactoring and test generation.
• Build automated test coverage (unit and integration).
• Collaborate with teams and stakeholders on scope and sequencing.
• Mentor less experienced developers and share modernization know-how.

Skills

C# / .NET

Legacy modernization

SOLID / clean architecture

SQL Server / data layer

AI-assisted development

Automated testing

Polish & English

Education

Computer science degree

Job description

Nexi Digital is seeking a Senior Software Engineer to drive the modernization of a payment platform by migrating a large ASP.NET WebForms/MVC monolith from .NET Framework 4.x to .NET 8, updating the data layer and integrations in an on-premise environment.

You will apply SOLID and clean-architecture principles, mentor the team, and leverage AI-assisted tools to accelerate analysis, refactoring and test generation in a hybrid work setup.