Senior Full Stack .NET Developer / Principal Backend EngineerLocation: Seattle, WA Position Type: Full-Time hybrid $180-200k+ + benefitsOverviewThis role serves as a senior technical leader responsible for driving backend architecture, guiding engineering best practices, and contributing across the full technology stack. The position focuses heavily on backend systems built with C# and .NET, while also supporting front-end integration efforts when needed. The engineer in this role will help shape the architectural vision, elevate engineering quality, and provide technical mentorship to the broader team.Key ResponsibilitiesBackend & Full-Stack DevelopmentDesign, develop, and maintain backend applications using C#,.NET Framework,.NET Core, and.NET 8Build and optimize REST APIs, including API versioning and BFF (Backend-for-Frontend) patternsLead data modeling and work extensively with SQL Server, including stored procedures, performance tuning, and Dapper (repository/unit-of-work patterns)Modernize or translate existing WPF components where neededImplement secure authentication flows such as OAuth2 and OpenIddict, including support for server-to-server interactionsCollaborate closely with front-end engineers to ensure seamless React/TypeScript integrationArchitecture & Technical LeadershipDrive the architectural direction across products, ensuring scalability, reliability, and maintainabilitySet and uphold high standards for engineering hygiene, code quality, and design practicesMentor senior and junior engineers, providing guidance in system design, coding practices, and problem-solvingTranslate complex technical topics into clear communication for both technical and non-technical stakeholdersIdentify, advocate for, and drive "delighter" features and improvements that enhance customer valueCloud, DevOps & InfrastructureLead the design and operation of large-scale cloud services using AWS (EC2 and related services) or other major public cloud platformsApply DevOps and security best practices across development and deployment workflowsUtilize containerization and orchestration technologies such as Docker and KubernetesContribute to evolving infrastructure that supports data workflows and emerging AI-related systemsCross-Functional CollaborationPartner with product, data, and engineering teams to shape technical strategies and deliver high-impact initiativesUnderstand user needs and customer workflows to inform system improvements and product directionOperate effectively in a fast-paced environment with high ambiguity, balancing technical and business prioritiesRequirementsRequired QualificationsBachelor's degree in Computer Science or a related field12+ years of experience building and operating large-scale cloud services or distributed systemsExpert-level proficiency in C# and the.NET ecosystem (.NET Framework, .NET Core,.NET 8)Strong experience with: SQL Server, relational databases, and performance optimizationREST API designDapper ORMOAuth2, OpenIddict, and modern authentication patternsDemonstrated experience with at least one major cloud provider (AWS, Azure, or GCP)Proficiency in at least one additional programming language (Java, TypeScript/JavaScript, Golang, Python, etc.)Experience with Docker, Kubernetes, or other container orchestration systemsAbility to work directly with end users or customers to understand requirements and user journeysStrong communication skills with the ability to clearly articulate technical decisions and trade-offsProven track record of developing technical strategies and executing them successfullyAbility to raise the engineering bar for quality, reliability, security, and maintainabilityDemonstrated success collaborating across teams and driving complex cross-functional initiativesNice-to-Have QualificationsStrong front-end experience with React and modern TypeScript frameworksExperience supporting or architecting infrastructure for AI pipelinesFamiliarity with NoSQL technologies, message queues, or event-driven architecturesExperience with WPF modernization or transition to web-based UI frameworksBenefitsCompetitive salary ($180-200+k) and performance-based bonus opportunities Comprehensive health, dental, and vision coverage Retirement plan options Generous paid time off and holiday schedule Professional development and continuing education support Flexible work arrangements where applicable