Senior Windows API & Browser Extension Developer

Position Name – Sr. Windows API & Browser Extension Developer Type of hiring – Subcon Location – Brampton, ON (100% onsite) Job Description: Role Overview We are seeking an experienced Senior Windows API & Browser Extension Developer to design, develop, and implement a secure Windows-based integration solution for a standalone enterprise environment. The solution will capture user-submitted data from a web portal through a Microsoft Edge browser extension and securely integrate it with downstream REST APIs using Windows Native Messaging or a locally hosted Windows service. The role requires hands-on experience in Windows application development, browser extension development, API integration, security engineering, and enterprise-grade software delivery. Key Responsibilities Design, develop, and deploy a secure Microsoft Edge (Chromium) browser extension for automated data capture and API integration workflows.Develop Windows-based integration components using C#, .NET Core, Windows Services, Win32 APIs, and Windows Native Messaging.Build and integrate secure REST APIs with support for API Keys, TLS/mTLS, certificate-based authentication, and secure communications.Design solutions to process sensitive business data entirely in memory, ensuring no transaction data is written to disk, logs, or diagnostic files.Implement robust error handling, retry mechanisms, timeout controls, status tracking, and resilience patterns for API interactions.Develop and support multi-user Windows Server / Terminal Services environments supporting concurrent user sessions.Configure and manage Windows security components including Certificate Store, DPAPI, service accounts, access controls, and secure secret management.Perform unit testing, integration testing, API testing, browser extension testing, and end-to-end system validation.Ensure compliance with Secure SDLC, secure coding standards, vulnerability scanning, code reviews, and security remediation requirements.Create and maintain HLD, LLD, deployment guides, operational runbooks, support documentation, and knowledge transfer materials.Collaborate with customer architects, security teams, infrastructure teams, and project stakeholders throughout the project lifecycle.Support deployment, production stabilization, warranty support, troubleshooting, and defect resolution activities.Package and deliver signed release artifacts, installation binaries, and deployment documentation for Windows Server environments. Mandatory Skills Windows Server 2019/2022 Administration & Development (Mandatory)Windows Terminal Services (RDS) Environment ManagementC#, .NET Core / ASP.NET CoreWindows API / Win32 DevelopmentMicrosoft Edge Extension Development (Manifest V3)Windows Native MessagingREST API Development & IntegrationTLS / mTLS / Certificate ManagementWindows Security, DPAPI, Certificate StoreSecure SDLC & OWASP Secure CodingGit/GitHub, CI/CD and Release ManagementUnit, Integration and End-to-End Testing Experience 8+ Years of Software Development experience.5+ Years of Windows Server, Windows Platform and .NET Development.3+ Years of Browser Extension and API Integration Development.Experience delivering secure enterprise solutions in Windows Server environments.Strong troubleshooting, documentation, and customer-facing communication skills.