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, Homes.com and Apartments.com. 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.

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.

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