Senior .NET Platform Engineer — AI & Observability

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

Benefits offered by this job

Healthcare coverage

401(k) with matching

Employee stock purchase plan

Tuition reimbursement

On-site fitness center

Job summary

CoStar Group in Arlington, VA, is seeking a Senior Software Engineer for the Platform Development team to build distributed API‑driven systems supporting CoStar's brands. You will design AI‑powered solutions and integrate AI agents, tools, and workflows to enhance product capabilities.

You'll collaborate with Product, Research, and Data teams, apply telemetry and observability, and push for code quality with evidence‑based improvements.

Qualifications

• Bachelor's degree from an accredited university.
• 5 years of deep .NET development (C#) with cross‑platform communication such as Web API.
• Experience with cloud platforms (AWS or Azure).
• Experience with RESTful services and ASP.NET MVC.
• Experience building large‑scale distributed systems in an agile environment.
• Data modeling experience.
• Familiarity with LLMs, prompt engineering, or agent architectures.
• Experience with monitoring, telemetry, observability, or automated diagnostics.

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, efficient, maintainable code using C#, .NET, SQL Server, AWS.
• Utilize telemetry to identify anomalies and performance bottlenecks.
• Lead software design, development standards, and code reviews.
• Collaborate with Product, Research, and Data teams to drive business value.

Skills

C# programming

NET Framework

RESTful APIs

Cloud: AWS/Azure

Data modeling

SQL/SQL Server

LLMs/AI concepts

Observability/Telemetry

Education

Bachelor's Degree in Computer Science or related field

Tools

ASP.NET MVC

Web API

SQL Server

AWS

Azure

Job description

CoStar Group in Arlington, VA, is seeking a Senior Software Engineer for the Platform Development team to build distributed API‑driven systems supporting CoStar's brands. You will design AI‑powered solutions and integrate AI agents, tools, and workflows to enhance product capabilities.

You'll collaborate with Product, Research, and Data teams, apply telemetry and observability, and push for code quality with evidence‑based improvements.