Senior .Net Engineer

N-iX; Kraków; Hybrid; PLN 180,000 - 240,000; Full time

Benefits offered by this job

Flexible working format

Professional development programs

Knowledge sharing culture

Job summary

N-iX is seeking a Senior .NET Engineer to migrate a client-facing e-commerce payment flow to a new provider. You will design an abstraction layer to support multiple providers and implement the integration with the new gateway, including card-capture and refunds, while minimizing PCI exposure.

The role requires 6+ years of professional .NET experience, deep C# and ASP.NET expertise across MVC, Web API and EF Core, and strong English communication.

Qualifications

• 6+ years of professional .NET development on large production systems.
• Must have brownfield / legacy modernization experience.
• Expert C# and ASP.NET (MVC, Web API, Razor Pages) across .NET Framework 4.5.x and .NET 6+ migrations; EF / EF Core.
• Security mindset with remediation of findings (OWASP, secrets handling, crypto); PCI/payments exposure is a plus.
• Fluent written and spoken English (B2+) for documentation and client calls.

Responsibilities

• Design an abstraction layer to decouple from a single payment provider to enable multiple providers.
• Implement integration with the new provider, including card-capture and refunds, while minimizing PCI exposure.
• Collaborate with a small delivery team and client-side stakeholders where ownership or documentation is incomplete.

Skills

6+ years .NET

C# & ASP.NET

MVC/Web API

EF / EF Core

Security/PCI

English B2+

Tools

OWASP

Job description

We are looking for a Senior .NET Engineer to work on migrating a client-facing e-commerce/store application's payment processing from its current gateway to a new payment provider.

Key Responsibilities

• Design and implement an abstraction layer that decouples the application from a single payment provider, enabling multiple providers to operate in parallel.
• Implement the integration with the new payment provider, including the card-capture and payment/refund flows, in a way that minimizes the application's compliance exposure.
• Collaborate closely with a small delivery team and client-side stakeholders where ownership or documentation is incomplete.

Requirements & Qualifications

• Experience: 6+ years of professional .NET development on large production systems; brownfield / legacy modernization experience is mandatory — this is not a greenfield role.
• Core stack (Must-Have): expert C# and ASP.NET (MVC, Web API, Razor Pages); hands-on with both .NET Framework 4.5.x-era code and .NET 6+ migrations; EF / EF Core.
• Security mindset: practical experience remediating security findings (OWASP classes, secrets handling, crypto usage) in existing code; PCI / payments / fintech exposure is a strong plus.
• English: fluent written and spoken English (B2+) for documentation, evidence packages and client calls.

We offer*:

• Flexible working format - remote, office-based or flexible
• A competitive salary and good compensation package
• Professional development tools (mentorship program, tech talks and trainings, centers of excellence, and more)
• Active tech communities with regular knowledge sharing