Full Stack .NET Developer

  About the Role Simon & Schuster, one of the world's leading publishers, is investing in a multi-year modernization of the core systems that power order management, fulfillment, partner integration, and financial transactions. We are replacing long-established technology with modern .NET and SQL solutions using an AI-assisted approach. The program is already delivering measurable performance improvements in production. The Full-Stack .NET Developer is the hands-on builder on the modernization team. You will take legacy batch programs and, working from documented business requirements, replace them with modern, production-grade .NET services and SQL solutions that are validated in parallel against the existing system before every cutover. As the program advances, the role extends to modern web front ends that replace legacy green-screen workflows, which is why full-stack capability matters. AI tooling is central to how this team works: AI assists with legacy analysis, code generation, test generation, and documentation. You will use these tools daily — and you will be expected to review, refine, and validate AI-generated code critically rather than accept it blindly. Key Responsibilities Build modern replacements — Implement .NET worker services, APIs, and T-SQL stored procedures that replace legacy COBOL batch programs while preserving required business behavior. Review and refine AI-generated code — Use AI-assisted development for speed, then apply engineering judgment: correctness, edge cases, error handling, performance, and maintainability are yours to guarantee. Implement target architecture patterns — Apply the program's established patterns: structured logging and run telemetry, configuration-driven behavior, parallel-run ("shadow") support, restartability, and clean integration contracts. Support validation and cutover — Instrument every replacement for reconciliation against legacy output; work with the QA / Test Automation Engineer to drive each package to a clean validation gate before production cutover. Resolve complex conversion issues — Debug behavioral differences between legacy and modern implementations, working with legacy specialists to understand what the original code actually does. Front-end development — Build and maintain modern web UI components as the program modernizes user-facing workflows (browser-based replacements for legacy green-screen transactions). Contribute to engineering standards — Capture lessons learned, improve shared frameworks and templates, and help raise the quality bar as the team scales. Required Qualifications 5+ years of professional full-stack .NET development — C#, .NET (modern .NET 6+ preferred), building and operating production services. Experience using AI tools to assist development — e.g., AI-assisted code generation, code review, test generation, or documentation — with the judgment to critically validate generated output before it ships. Strong SQL Server / T-SQL skills — stored procedures, set-based logic, transactions, and query-performance fundamentals. Back-end service experience — background/worker services, scheduled or batch processing, structured logging, and configuration management. Front-end web development experience — modern web UI with ASP.NET Core (Razor/Blazor) or a JavaScript/TypeScript framework (React, Angular, or similar). Production mindset — experience owning code that runs unattended in production: error handling, restartability, observability, and safe deployment practices. Strong debugging and problem-solving skills, including reasoning about data-level differences between two systems. Clear written communication — design notes, code review feedback, and operational documentation. Preferred Qualifications Experience on a legacy-modernization, system-replacement, or platform-migration program. Exposure to legacy or mainframe-style environments (e.g., COBOL-era batch systems) — enough familiarity to work effectively with legacy specialists when analyzing existing behavior. No COBOL programming required. Order processing, fulfillment, supply-chain, or EDI domain experience. Data-access frameworks such as Dapper or Entity Framework Core. Batch scheduling environments (AutoSys or similar) and overnight batch operations. Azure experience — SQL Server on Azure VMs, Azure SQL Managed Instance, or Azure-hosted services. Automated testing practices — unit testing, integration testing, or test-driven development. What Success Looks Like Replacement packages move through build and validation at a steady cadence, passing reconciliation against legacy output with few surprises. AI-assisted speed without AI-assisted defects: generated code is consistently caught, corrected, and hardened before it reaches production. Replacements demonstrate measurable improvements — faster runtimes, fewer failures, less database contention — over the legacy processes they retire. Shared patterns and lessons learned make each successive package cheaper and safer than the last.