Senior .NET Engineer: Modernize a Payment Platform (Hybrid)

Reply Group; Katowice; Hybrid; PLN 180,000 - 320,000; Full time

Benefits offered by this job

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Job summary

Nexi Digital is seeking a Senior Software Engineer in Poland to lead the modernization of a payment platform. You will migrate a large ASP.NET WebForms/MVC monolith from .NET Framework 4.x to .NET 8, upgrade the data layer, and align integrations in an on-premise environment.

You will work with AI-assisted tools to accelerate analysis, refactor toward SOLID and clean architecture, and mentor colleagues while delivering safe, incremental migrations. Hybrid work model.

Qualifications

• Successfully completed university degree in computer science or a comparable field of study.
• 6+ years of commercial software development experience.
• Extensive experience with C# and .NET across generations — both .NET Framework 4.x (ASP.NET WebForms/MVC) and modern .NET (6/8) with ASP.NET Core.
• Hands-on experience with modernizing or migrating legacy applications (re-platforming, incremental refactoring, strangler-fig-style approaches).
• Strong knowledge of software design principles and patterns, including SOLID and clean architecture.
• Solid experience with Microsoft SQL Server and data-layer refactoring.
• Practical experience with AI-assisted development (e.g. GitHub Copilot or similar LLM-based tools).
• Experience with automated unit and integration testing.
• Fluency in Polish and very good communication in English.
• Availability to work in a hybrid mode. Remote workers, we invite to the office once every month.

Responsibilities

• Analyzing the legacy codebase and shaping an incremental, low-risk migration path (module by module, no big-bang rewrites).
• Designing and implementing the migration of application components from .NET Framework 4.x / ASP.NET (WebForms, MVC) to .NET 8 / ASP.NET Core.
• Refactoring the code towards SOLID principles and clean architecture as part of the migration, not as a separate project.
• Modernizing the Microsoft SQL Server data layer and the platform's integrations with surrounding systems.
• Using AI-assisted development tools to accelerate legacy code analysis, refactoring and test generation.
• Building the automated test coverage (unit, integration) that makes the migration verifiable at every step.
• Collaborating closely with the development teams and stakeholders on scope, sequencing and technical decisions.
• Mentoring less experienced developers and sharing modernization know-how across the team.

Skills

C# & .NET

Software architecture

Legacy modernization

SQL Server

AI-assisted development

Unit testing

English communication

Polish fluency

Education

CS degree or comparable field

Tools

GitHub Copilot

ASP.NET Core

ASP.NET WebForms/MVC

Microsoft SQL Server

Job description

Nexi Digital is seeking a Senior Software Engineer in Poland to lead the modernization of a payment platform. You will migrate a large ASP.NET WebForms/MVC monolith from .NET Framework 4.x to .NET 8, upgrade the data layer, and align integrations in an on-premise environment.

You will work with AI-assisted tools to accelerate analysis, refactor toward SOLID and clean architecture, and mentor colleagues while delivering safe, incremental migrations. Hybrid work model.