SENIOR SOFTWARE .NET ENGINEER

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

Benefits offered by this job

Medical care

Benefits platform

Training opportunities

Language courses platform

Company events

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

As a Senior Software Engineer at Nexi Digital, you will drive the modernization of an established, business-critical payment platform — migrating a large ASP.NET (WebForms/MVC) monolith from .NET Framework 4.x to .NET 8, together with its database layer and system integrations, in an on-premise environment. You will combine deep .NET craftsmanship with modern, AI-assisted ways of working to make the migration faster and safer.

• 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 (e.g. GitHub Copilot and LLM-based tooling) to accelerate legacy code analysis, refactoring and test generation — and helping the team adopt these practices responsibly
• 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
• MEDICAL CARE
• BENEFITS PLATFORM
• TRAINING OPPORTUNITIES
• LANGUAGE COURSES PLATFORM
• COMPANY EVENTS
• Motivizer Benefits Platform to choose and manage all your benefits in one place. You receive a budget (550 PLN monthly). You can choosemedical care package, meal tickets, sports cards (we have Multisport and on preferential terms, we have membership cards to one of the most popular Gyms),cinema tickets, shop vouchers, discounts and many more.
• Language Courses –you'll have access to a multi-language learning platform enabling you to practice you language skills and learn new ones!
• Regular and systematic furthertraining opportunities - both internallyand from external providers. We support your ongoing learning and development.
• Cooperation within an internal community is our everyday reality. We havenetworking events, coding challenges, and company parties for different occasions.

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) as part of your daily engineering workflow
• 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

About Nexi Digital

Nexi is Europe's PayTech company operating in high-growth, attractive European markets and technologically advanced countries. Listed on Borsa Italiana's MTA, Nexi has the scale, geographic reach and abilities to drive the transition to a cashless Europe. With its portfolio of innovative products, e-commerce expertise and industry-specific solutions, Nexi provides flexible support for the digital economy and the entire payment ecosystem globally, across a broad range of different payment channels and methods. Nexi’s technological platform and the best-in-class professional skills in the sector lets the company operate at its best in three market segments: Merchant Services & Solutions, Cards & Digital Payments and Digital Banking & Corporate Solutions. Nexi constantly invests in technology and innovation, focusing on two fundamental principles: meeting, together with its partner banks, customer needs and creating new business opportunities for them. Nexi is committed to supporting people and businesses of all sizes, transforming the way people pay and businesses accept payments. It offers companies the most innovative and reliable solutions to better serve their customers and expand. By simplifying payments and enabling people and businesses to build closer relationships and grow together, Nexi promotes progress to benefit everyone.