Senior .Net Full-Stack Engineer (with Angular or React)

We are looking for a Senior .NET Full-Stack Engineer to execute security remediation and version upgrades across the five in-scope applications. This is backend-leaning brownfield engineering at its most concentrated: fixing real vulnerability classes flagged by penetration testing and code review (hard-coded secrets and keys, weak or reversible cryptography, token and session handling, injection, sensitive-data logging), and lifting .NET Framework 4.5.x-era codebases to supported patch levels - and to .NET 6+/8 where feasible without material rework - together with their front-end dependency stacks (React 18, Angular, TypeScript, Telerik / Kendo).

Key Responsibilities:

• Remediate security findings across ASP.NET (MVC, Web API, Razor Pages) codebases; every fix ships QA-validated, with tests and a rollback runbook, through the client's CI/CD.
• Execute dependency and framework upgrades (.NET Framework 4.8.1, .NET 8, EF / EF Core, React 18, Angular 20, Telerik / Kendo current release, SignalR) with regression checks; document residual gaps per component.
• Navigate and reverse-engineer legacy code - one application includes Classic ASP / VBScript tiers - to trace data and payment flows; AI-assisted code discovery is a standard part of the toolkit.
• Pair with the client's retained engineering team; knowledge coverage is uneven (one application has no SME at all), so comfort working from code rather than documentation is essential.
• Contribute evidence to the retest and closure cycle: before / after artifacts, scan diffs, deployment logs.
• Immediate start for a focused 3-month initial engagement dedicated to Azure/AWS security hardening and system upgrades, working directly with CTO leadership. High-performing execution opens the door to Phase 2 (long-term re-architecture and platform integration).

Requirements:

• 6+ years of professional .NET development on large production systems; brownfield / legacy modernization experience is mandatory — this is not a greenfield role.
• 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.
• Solid Angular, React and TypeScript for upgrading and stabilizing existing UIs.
• Practical experience remediating security findings (OWASP classes, secrets handling, crypto usage) in existing code; PCI / payments / fintech exposure is a strong plus.
• Azure PaaS (App Services, Functions, Service Bus, Cosmos DB); AWS (Lambda, S3, SNS/SQS); Azure AD B2C; Blazor; SignalR; Telerik / Kendo UI.