Senior .NET Developer

About Rentsync: Rentsync is an award-winning, high-growth organization that provides high quality websites, marketing services, and software solutions to the rental and property management industry throughout Canada and the United States. About the Role: As our Senior .NET Developer you’ll architect and ship cloud-native APIs on .NET 8+ and Azure, set the engineering standard across the team, and lead how we put AI development tools to work on real code every single day. This is a seat for an engineer who thinks like a product owner rather than a ticket-taker, and who wants to raise the bar for everyone around them. This is a hybrid/remote position, all qualified candidates are encouraged to apply, however preferential consideration may be given to individuals who can report to one of Rentsync’s regional offices (located in Toronto, St. Catharines and Montreal) 2 days per week on average. Duties & Responsibilities: Take full technical ownership of server-side logic and database structures — develop, maintain, and optimize them for performance and reliability. Take a product-oriented approach to development: understand product goals and user needs, and propose solutions that deliver real business value. Design and implement RESTful APIs and other web services to support front-end functionality, based on descriptions from the product team. Drive architecture decisions and uphold Clean Architecture, CQRS, and engineering standards across the team. Lead the adoption and day-to-day use of AI development tools on real projects, and mentor the team in using them effectively. Create and support Kubernetes configuration, deploy and run containerized services, and monitor their health and performance. Collaborate with front-end developers, the QA team, and product managers to meet functional and non-functional requirements. Implement data security and protection measures, including the safe handling of PII and other sensitive data. Mentor mid-level and junior developers and raise the technical bar through code reviews and knowledge sharing. Troubleshoot, debug, and resolve issues in production and development environments. Stay current with emerging back-end technologies and best practices. Essential Knowledge, Skills & Abilities: Modern .NET engineering fundamentals: Clean Architecture, CQRS / MediatR, and Domain-Driven Design. Microsoft Azure platform: Compute Services, Azure SQL Database, Service Bus, Storage, Entra ID, Key Vault, and Application Insights. Kubernetes (K8s) concepts and configuration (manifests / Helm) and the operation of containerized services. SQL Server internals: schema and index design, execution-plan analysis, transactions, and concurrency. Secure handling of PII and other sensitive data. Expert-level Entity Framework Core: advanced querying, performance tuning, and migrations. Modern C# patterns (C# 12+): primary constructors, records, nullable reference types, and source generators. Advanced T-SQL and query tuning. Authoring and supporting Kubernetes manifests and Helm; deploying and operating containerized services; monitoring health, logs, and resource usage. Deploying to the cloud via DevOps pipelines. Daily, fluent use of AI development tools (e.g., GitHub Copilot, Claude Code, Cursor). Security-focused code review — spotting code and data-handling problems during reviews. Review, verify, and safely ship AI-generated code — and raise the whole team’s effectiveness with these tools. Design and operate cloud-native solutions. Take full technical ownership of design, delivery, and quality. Mentor developers, lead code review, and set and uphold engineering standards. Translate product goals and user needs into technical solutions — and proactively propose better ones. Troubleshoot, debug, and resolve issues across production and development environments. Essential Qualifications: 8+ years of professional experience with modern .NET / .NET Core, building APIs for business-oriented projects. 2+ years carrying full technical ownership of design, delivery, and quality. Located in and legally entitled to work in Canada Additional Preferred Qualifications: 2+ years of professional experience mentoring or leading junior developers Hands-on experience integrating LLMs into .NET. Able to work in one of Rentsync's regional offices (Toronto, Montreal or St. Catharines) 2-3 days per week on average Rentsync is an equal opportunity employer. If you are selected to participate in the interview process and require unique accommodations, please don’t hesitate to let us know. Successful candidates may be required to complete a criminal background check in the final phase of the interview process.