Senior Full Stack Engineer

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

Benefits offered by this job

Healthcare coverage

401(k) retirement plan with matching

Employee stock purchase plan

Paid time off

Tuition reimbursement

Job summary

CoStar Group, a leading real estate data provider, is seeking a Senior Full Stack Engineer in Arlington, VA. The role focuses on expanding the data platform across CoStar Suite, LoopNet, Homes.com, and Apartments.com, with AI-driven features and robust cloud infrastructure.

You will work in a hybrid model (in office Mon-Thu, remote Fri) and contribute to scalable systems using TypeScript, C#, .NET, and AWS while shaping product capabilities with AI integrations.

Qualifications

• Bachelor’s degree from an accredited university.
• 3+ years of deep .NET (C#) development including web APIs and services.
• 5+ years of TypeScript with modern frontend and backend JS tooling (Node, Vite, React).
• Experience with Terraform and IaC practices.
• Cloud experience on AWS or Azure.
• Experience building large-scale distributed systems in agile environments.
• Familiarity with LLMs, context engineering, or agent-based architectures.

Responsibilities

• Build big, distributed, API-driven systems for tens of thousands of users.
• Integrate AI skills, agents, tools, and workflows across platforms and products.
• Produce robust, maintainable code using TypeScript, C#, .NET, SQL Server, AWS.
• Develop customer-facing and internal web apps with React/TypeScript.
• Use AI to improve monitoring, observability, and diagnostics; reduce risk.
• Lead software design, standards, and code reviews.
• Collaborate with Product, Research, and Data teams on AI-driven value.

Skills

TypeScript

C#

React

AWS

Terraform

Kubernetes

Datadog

LLMs familiarity

Observability

AI awareness

Education

Bachelor’s Degree

Tools

Terraform

Kubernetes

DynamoDB

SQS

Kafka

Datadog

Job description

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.

Responsibilities

• 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.

Basic Qualifications

• 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 diagnostics platforms.
• Strong understanding of data quality principles, data governance concepts, and data-centric application design.

Preferred Qualifications and Skills

• Strong communication skills (to both business and technical partners).
• Experience with React Router Framework and Effect.
• SQL and database development knowledge.
• Experience using observability and APM platforms like Datadog.
• Familiarity with services such as Kafka, DynamoDB, and SQS.
• Experience with deploying to Kubernetes, EKS, and ECS.
• Data modeling experience from conceptual, logical, and physical designs.
• Experience implementing MCP clients and servers, workflow automation platforms, or intelligent search solutions.
• Experience applying AI-assisted software development practices to improve engineering productivity and code quality.

What’s in it for You

• Comprehensive healthcare coverage: Medical / Vision / Dental / Prescription Drug
• Life, legal, and supplementary insurance
• Virtual and in person mental health counseling services for individuals and family
• Commuter and parking benefits
• 401(K) retirement plan with matching contributions
• Employee stock purchase plan
• Paid time off
• Tuition reimbursement
• On-site fitness center and/or reimbursed fitness center membership costs (location dependent)
• Access to CoStar Group’s Employee Resource Groups
• Complimentary gourmet coffee, tea, hot chocolate, fresh fruit, and other healthy snacks

Base Compensation: $143,000 - $187,000 Annually

We welcome all qualified candidates who are currently eligible to work full-time in the United States to apply. However, please note that CoStar Group is not able to provide visa sponsorship for this position.

CoStar Group is an Equal Employment Opportunity Employer; we maintain a drug-free workplace and perform pre-employment substance abuse testing.