Senior Full Stack Engineer

Senior Full Stack Engineer Job Description Overview CoStar Group (NASDAQ: CSGP) is a leading global provider of commercial and residential real estate information, analytics, and online marketplaces. Included in the S&P 500 Index, CoStar Group is on a mission to digitize the world’s real estate, empowering all people to discover properties, insights and connections that improve their businesses and lives. We have been living and breathing the world of real estate information and online marketplaces for over 35 years, giving us the perspective to create truly unique and valuable offerings to our customers. We’ve continually refined, transformed and perfected our approach to our business, creating a language that has become standard in our industry, for our customers, and even our competitors. We continue that effort today and are always working to improve and drive innovation. This is how we deliver for our customers, our employees, and investors. By equipping the brightest minds with the best resources available, we provide an invaluable edge in real estate. As a Senior Software Engineer on the Platform Development team, you will play a key role in expanding the data platform that supports all of CoStar Group’s largest brands including CoStar Suite, LoopNet, and . You will deeply understand what drives the business for which you are building software. We firmly believe that what separates a good developer from a great one is a deep understanding of the business that they are supporting. CoStar is investing heavily in artificial intelligence to accelerate software delivery, improve platform observability, automate research and business workflows, enhance product experiences through intelligent agents and skills, and improve data quality across enterprise systems. Successful candidates will demonstrate a willingness to learn, adopt, and apply AI technologies responsibly to solve complex business and engineering challenges. This position is located in Arlington, VA and is in office Monday through Thursday with work from home on Friday. Responsibilities Build big, distributed, API-driven systems for tens of thousands of users. Build and integrate AI skills, agents, tools, and intelligent workflows into internal systems and customer-facing applications across CoStar brands, improving platform intelligence and unlocking new product capabilities. Produce code that is robust, efficient, and maintainable; our primary tools are TypeScript, C#, .NET, SQL Server, AWS. Build and maintain customer-facing and internal web applications using React/TypeScript. Utilize AI models to enhance monitoring, replayability, observability, and diagnostic capabilities to improve system reliability, accelerate problem resolution, and reduce operational risk. Drive and lead software design, development standards, and code review practices. Collaborate with Product, Research, and Data teams to identify opportunities where AI-driven workflows and automation can create business value and improve decision-making. Basic Qualifications Bachelor’s Degree required from an accredited, not for profit, in person, university or college. A track record of commitment to prior employers. 3+ years of deep .NET development (C#) development experience such as web APIs, background services, and developing and publishing shared packages. 5+ years of experience with TypeScript and modern frontend and backend JS tooling (e.g. Node, Vite, React, etc.). Experience with Infrastructure as Code (IaC) tools such as Terraform. Working knowledge and experience with cloud-based platforms (AWS or Azure). Experience in architecting, designing, and building large-scale distributed, service-oriented systems and web applications in an agile environment. Familiarity with using large language models (LLMs), context engineering, or agent-based architectures. Experience working with monitoring, telemetry, observability, or automated diagnostics platforms. Strong understanding of data quality principles, data governance concepts, and data-centric application design. Preferred Qualifications and Skills Strong communication skills (to both business and technical partners). Experience with React Router Framework and Effect. SQL and database development knowledge. Experience using observability and APM platforms like Datadog. Familiarity with services such as Kafka, DynamoDB, and SQS. Experience with deploying to Kubernetes, EKS, and ECS. Data modeling experience from conceptual, logical, and physical designs. Experience implementing MCP clients and servers, workflow automation platforms, or intelligent search solutions. Experience applying AI-assisted software development practices to improve engineering productivity and code quality. What’s in it for You When you join CoStar Group, you’ll experience a collaborative and innovative culture working alongside the best and brightest to empower our people and customers to succeed. We offer you generous compensation and performance-based incentives. CoStar Group also invests in your professional and academic growth with internal training, and tuition reimbursement. Our benefits package includes (but is not limited to): Comprehensive healthcare coverage: Medical / Vision / Dental / Prescription Drug Life, legal, and supplementary insurance Virtual and in person mental health counseling services for individuals and family Commuter and parking benefits 401(K) retirement plan with matching contributions Employee stock purchase plan Paid time off Tuition reimbursement On-site fitness center and/or reimbursed fitness center membership costs (location dependent) Access to CoStar Group’s Employee Resource Groups Complimentary gourmet coffee, tea, hot chocolate, fresh fruit, and other healthy snacks The final salary or hourly rate offered for this role will fall within the range set forth below based on a variety of factors, including but not limited to, geographic location, skills, and competencies. Base Compensation: $143,000 - $187,000 Annually We welcome all qualified candidates who are currently eligible to work full-time in the United States to apply. However, please note that CoStar Group is not able to provide visa sponsorship for this position. #LI-AR CoStar Group is an Equal Employment Opportunity Employer; we maintain a drug-free workplace and perform pre-employment substance abuse testing