Staff Full Stack Engineer

ATG connects thousands of auction houses, listing millions of items worth over $15 billion annually (and growing!), to buyers in over 170 countries around the world. These buyers generate over 100 million bids a year for our sellers, helping them achieve maximum value for the goods they sell. We help auctioneers sell everything from medieval swords to combine harvesters, paintings and decorative art through to classic cars, furniture, and Caterpillar forklifts. We do this through 8 marketplaces that leverage our online auction technologies. We make auctioneers more efficient; we make small companies big by bringing them access to millions of bidders they could never find on their own, and we bring them technology they could never afford alone. We bring bidders choice of unique and specialized items, convenience, and trust. And we do it all in a shared success model that accelerates growth of the circular economy and sustainable buying. With ATG, our buyers and sellers win but so too does the planet! We have ethical ambition and it’s something our employees value and is a key part of who we are….as well as being a high growth marketplace company with excellent competitive positioning!

What you will do

As a Senior Full Stack Software Engineer at ATG, you will be part of a collaborative agile team focused on delivering high-value, high-performance solutions across both customer-facing web applications and the services that power them. You will work across modern React and TypeScript front ends and C#/.NET Core backend systems, building scalable, reliable software for a high-transaction e-commerce platform.

You understand that quality is everyone’s responsibility. You will work closely with Product, Design, QA, SDETs, and Engineering teammates to design, build, test, deploy, and support meaningful enhancements that improve the customer experience and strengthen the platform behind it. Your team will be expected to take ownership of the products and services you work on and actively embrace improving how outcomes are achieved. You will also have meaningful opportunities to influence engineering practices, mentor others, and help ATG continue to expand, integrate, and build new products.

By giving millions of items second, third, and even infinite lives, we are accelerating the growth of the circular economy and creating a new global channel of sustainable commerce.

Key Responsibilities

• Design, develop, test, deploy, and support full stack features and systems.
• Build modern user experiences using React and TypeScript.
• Design and implement high-performance, scalable, multi-threaded, and complex backend services using C# and .NET Core.
• Collaborate early and often with teammates and stakeholders to understand feature scope, shape solutions, and refine stories and acceptance criteria.
• Contribute to architecture, engineering standards, and patterns that improve performance, maintainability, reliability, and developer productivity.
• Build, improve, and operate true CI/CD pipelines that enable safe, fast, and repeatable delivery.
• Write unit and other automated tests as part of a quality-first engineering culture.
• Work with SQL and relational databases to design, query, and optimize data access patterns.
• Pair program, review code, and support teammates in raising the quality bar across the team.
• Partner effectively with QA and SDETs to support robust end-to-end test coverage where appropriate.
• Document and communicate the systems, decisions, and learnings that help the wider engineering organization move faster.

Key Requirements

• Collaboration and innovation.
• Strong analytical and problem-solving skills, with excellent attention to detail.
• The ability to multitask and remain calm and focused in a demanding environment.
• Strong verbal and written communication skills, including the ability to communicate effectively with technical leaders and cross-functional partners.
• A strong sense of ownership, accountability, and continuous improvement.

What you need for success

• Bachelor’s degree in computer science or related field, or equivalent technical experience.
• 8+ years of professional software engineering experience, including meaningful full stack development experience.
• Senior-level experience with C# and .NET Core.
• Senior-level experience with modern React and TypeScript.
• Experience building high-performance, scalable, multi-threaded backend services in complex production environments.
• Experience building and maintaining true CI/CD pipelines.
• Strong experience writing unit tests and contributing to automated quality practices.
• Strong experience with SQL and relational databases.
• Experience working on high-traffic, customer-facing applications in production environments.

Customer-focused approach.

• Expert ability to debug issues across the full stack, from UI through services and data layers.
• Interest in learning and applying emerging AI-enabled engineering approaches where they create practical value.

Nice to have

• Experience writing automated tests in Playwright with TypeScript and/or supporting SDETs in creating and maintaining those test suites.
• Familiarity with AI tools, agentic AI workflows, MCPs, and agent orchestration.
• E-commerce or marketplace experience.
• Experience building for different audiences, including accessibility and internationalization.
• Experience mentoring engineers and helping elevate team engineering practices.