Senior C#/.NET Engineer — AI‑Driven, Large‑Scale APIs (Hybrid)

CoStar Group; Arlington (VA); Hybrid; USD 143,000 - 187,000; Full time

Benefits offered by this job

Health insurance

401(k) with matching

Employee stock purchase plan

Tuition reimbursement

Commuter benefits

Job summary

CoStar Group in Arlington, VA is seeking a Senior Software Engineer (C#/.NET) to build large, distributed systems and AI‑powered features. The role expects collaboration with Product, Research, and Data teams to deliver robust, scalable software across CoStar brands.

Responsibilities include designing AI workflows, advancing telemetry, and leading code reviews in an agile environment. Hybrid work model and in‑office presence required (Mon–Thu in office, Fri remote).

Qualifications

• 5+ years of deep .NET development (C#) experience.
• Cloud platform experience (AWS or Azure).
• RESTful services and ASP.NET MVC experience.
• Familiarity with large language models (LLMs) and AI agents.

Responsibilities

• Build big, distributed, API‑driven systems for tens of thousands of users.
• Design and implement AI‑powered software solutions across CoStar brands.
• Build and integrate AI skills, agents, tools, and intelligent workflows.
• Produce robust, maintainable code using C#, .NET Framework, SQL Server, AWS.
• Utilize telemetry, monitoring, and observability to improve reliability.
• Implement telemetry‑driven solutions to identify anomalies and bottlenecks.
• Drive software design standards and code reviews.
• Develop automation to streamline research workflows and information discovery.
• Collaborate with Product, Research, and Data teams to create business value.
• Evaluate emerging technologies to strengthen the platform and practices.

Job description

CoStar Group in Arlington, VA is seeking a Senior Software Engineer (C#/.NET) to build large, distributed systems and AI‑powered features. The role expects collaboration with Product, Research, and Data teams to deliver robust, scalable software across CoStar brands.

Responsibilities include designing AI workflows, advancing telemetry, and leading code reviews in an agile environment. Hybrid work model and in‑office presence required (Mon–Thu in office, Fri remote).