Senior .Net Engineer

Role Overview 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.Nice-to-Haves: Azure PaaS (App Services, Functions, Service Bus, Cosmos DB); AWS (Lambda, S3, SNS/SQS); Azure AD B2C; Blazor; SignalR; Telerik / Kendo UI.English: fluent written and spoken English (B2+) for documentation, evidence packages and client calls. We offer*: Flexible working format - remote, office-based or flexibleA competitive salary and good compensation packagePersonalized career growthProfessional development tools (mentorship program, tech talks and trainings, centers of excellence, and more)Active tech communities with regular knowledge sharingEducation reimbursementMemorable anniversary presentsCorporate events and team buildingsOther location-specific benefitsnot applicable for freelancers