Senior C#/.NET Engineer — AI-Driven Platform

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

Benefits offered by this job

Healthcare

401K with matching

Tuition reimbursement

Employee stock purchase plan

Paid time off

On-site fitness center

Employee Resource Groups

Snacks and beverages

Job summary

CoStar Group, located in Arlington, VA, is seeking a Senior Software Engineer to extend the data platform across its brands. The role emphasizes building distributed, API-driven systems with C#, .NET, SQL Server, and AWS, while integrating AI agents and automation to improve intelligence and efficiency.

You will collaborate with Product, Research, and Data teams and help define standards for scalable, observable services in an Agile environment.

Qualifications

• Bachelor’s Degree from an accredited university.
• 5+ years of deep .NET development (C#) with Web API.
• MSSQL or other relational database development experience.
• Cloud platforms (AWS or Azure) experience.
• RESTful web services and ASP.NET MVC experience.
• Experience building large-scale distributed, service-oriented systems in an agile environment.
• Data modeling experience.
• Familiarity with LLMs, prompt engineering, or agent-based architectures.
• Experience with monitoring, telemetry, observability, or diagnostics platforms.
• Strong understanding of data quality principles and data governance.

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 bullet-proof code using C#, .NET Framework, SQL Server, AWS.
• Utilize AI models to enhance monitoring, observability, and diagnostics.
• Implement telemetry-driven solutions to identify anomalies and bottlenecks.
• Lead software design, development standards, and code reviews.
• Build intelligent automation to streamline research workflows.
• Collaborate with Product, Research, and Data teams to identify AI-driven value.
• Evaluate emerging technologies to strengthen the platform and practices.

Skills

C# / .NET development

Distributed systems design

RESTful services

Cloud platforms (AWS/Azure)

MSSQL / relational DB

AI/LLMs familiarity

Telemetry & observability

Education

Bachelor's Degree

Tools

SQL Server

Web API

AWS

Azure

Job description

CoStar Group, located in Arlington, VA, is seeking a Senior Software Engineer to extend the data platform across its brands. The role emphasizes building distributed, API-driven systems with C#, .NET, SQL Server, and AWS, while integrating AI agents and automation to improve intelligence and efficiency.

You will collaborate with Product, Research, and Data teams and help define standards for scalable, observable services in an Agile environment.