Principal Engineer, ML

We exist to wow our customers. We know we’re doing the right thing when we hear our

customers say, “How did we ever live without Coupang?” Born out of an obsession to make shopping, eating, and living easier than ever, we’re collectively disrupting the multi-billion- dollar e-commerce industry from the ground up. We are one of the fastest-growing e-commerce companies that established an unparalleled reputation for being a dominant and reliable force in South Korean commerce.

We are proud to have the best of both worlds — a startup culture with the resources of a large global public company. This fuels us to continue our growth and launch new services at the speed we have been since our inception. We are all entrepreneurial surrounded by opportunities to drive new initiatives and innovations. At our core, we are bold and ambitious people that like to get our hands dirty and make a hands-on impact.

At Coupang, you will see yourself, your colleagues, your team, and the company grow every day

Our mission to build the future of commerce is real. We push the boundaries of what’s possible to solve problems and break traditional tradeoffs. Join Coupang now to create an epic experience in this always-on, high-tech, and hyper-connected world.

Coupang is seeking a Principal Engineer to define and lead the technical vision for our Ads Serving & ML Platform, one of the company's most critical business systems powered by large-scale machine learning and AI. Advertising plays a vital role in Coupang's ecosystem, enabling customers to discover relevant products while helping advertisers grow their businesses. The Ads platform directly influences customer engagement, advertiser success, and long-term revenue growth at massive scale.

As a Principal Engineer, you will own the architecture and technical strategy of the end-to-end ads serving ecosystem, spanning retrieval, ranking, auction, targeting, machine learning infrastructure, and online serving systems. You will identify future technology investments, drive innovation across organizational boundaries, and ensure that our platform continues to scale in performance, reliability, intelligence, and efficiency.

This is a highly influential individual contributor role requiring exceptional technical depth, strategic thinking, and cross-functional leadership. You will partner with engineering, machine learning, product, and business leaders to solve some of the most challenging problems in large-scale distributed systems and AI-powered advertising.

• →Define and drive the long-term technical vision, architecture, and strategy for Coupang's Ads Serving & ML Platform.
• →Lead the design and evolution of large-scale ad serving systems, including retrieval, ranking, auction, targeting, pacing, and measurement.
• →Drive platform modernization and adoption of emerging technologies, including large language models, generative AI, real-time inference, and next-generation ML infrastructure.
• →Identify and lead strategic technical investments that improve advertiser outcomes, customer experience, system scalability, and operational efficiency.
• →Partner with engineering, machine learning, product, and business leaders to align technical direction with company priorities and business objectives.
• →Influence architecture and engineering excellence across multiple organizations through technical leadership, design reviews, and mentorship.
• →Establish best practices for platform reliability, performance, scalability, observability, and operational excellence.
• →Drive measurable business impact through innovations that improve engagement, conversion, relevance, advertiser ROI, revenue growth, system efficiency and cost.
• →Serve as a recognized technical leader and domain expert in large-scale advertising systems and machine learning platforms.

• 12+ years of experience building large-scale software platforms, machine learning systems, or distributed infrastructure.
• Proven track record of architecting and operating mission-critical, high-throughput online systems at internet scale.
• Deep expertise in one or more user-facing machine learning domains, including advertising, search, recommendations, or personalization.
• Strong understanding of modern machine learning systems, including model training, feature engineering, experimentation, online inference, evaluation, and production operations.
• Experience building and scaling AI/ML serving infrastructure, including optimization of GPU- and CPU-based systems for latency, throughput, and cost efficiency.
• Strong understanding of large language models (LLMs), foundation models, retrieval-augmented generation (RAG), and production AI serving architectures.
• Deep knowledge of retrieval and ranking systems, including: 
  • Relevance and personalization
  • Candidate generation and ranking
  • Precision, recall, latency, and cost trade-offs
  • Online experimentation and model evaluation
• Demonstrated ability to drive significant business impact through technical innovation and platform evolution.
• Exceptional ability to influence technical direction across multiple teams and organizations without direct authority.
• Strong software engineering skills in Java, C++, or Python.
• Experience developing distributed systems that process and serve large-scale datasets with high availability and low latency.
• MS or above in Computer Science, Engineering, or a related technical discipline.

• Experience building large-scale advertising platforms, ad ranking systems, auction systems, or sponsored search products.
• Experience in e-commerce, marketplaces, or consumer internet companies operating at significant scale.
• Expertise in real-time machine learning, recommendation systems, search infrastructure, or large-scale personalization platforms.
• Proven contributions to architectural transformations or platform modernization initiatives across large organizations.
• Strong passion for exploring emerging technologies and translating innovation into business value.
• Experience working in high-growth, fast-scaling technology companies.
• PhD in Computer Science, Machine Learning, Artificial Intelligence, or related fields.