Senior Software Engineer (C#/.NET) - Hybrid AI Platform

CoStar Group

Virginia (MN)

On-site

USD 143,000 - 187,000

Full time

14 days+

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Benefits offered by this job

Healthcare coverage

401(k) matching

Stock purchase plan

Paid time off

Tuition reimbursement

Job summary

CoStar Group is seeking a Senior Software Engineer (C#/.NET) to expand the data platform powering CoStar Suite, LoopNet, Homes.com and Apartments.com. You will build distributed, API-driven systems and design AI-powered solutions to enhance product capabilities.

The role requires deep .NET expertise, cloud experience (AWS/Azure), and data modeling, with a focus on reliability, observability, and scalable architecture. Arlington, VA—in-office Mon-Thu, optional remote Friday.

Qualifications

Bachelor’s Degree from an accredited institution.
5+ years of deep .NET development (C#) experience with Web API.
Experience with cloud platforms (AWS or Azure).
Experience with RESTful web services and ASP.NET MVC.
Experience designing large-scale distributed systems in agile environments.
Data modeling experience.
Familiarity with LLMs, prompt engineering, or agent-based architectures.
Experience with monitoring, telemetry, observability or diagnostics platforms.
Strong data governance and data quality understanding.

Responsibilities

Build big, distributed, API-driven systems for tens of thousands of users.
Design AI-powered software to enhance customer experience and platform intelligence.
Integrate AI skills, agents, tools, and intelligent workflows into systems.
Produce robust, scalable code using C#, .NET Framework, SQL Server, AWS.
Use telemetry to identify anomalies and performance bottlenecks.
Lead software design, development standards, and code reviews.
Collaborate with Product, Research and Data teams on AI-driven value.