Senior Software Engineer I, Machine Learning, Search Systems

Company Description Etsy is the global marketplace for unique and creative goods. We build, power, and evolve the tools and technologies that connect millions of entrepreneurs with millions of buyers around the world. As an Etsy employee, you will tackle unique, meaningful, and large-scale problems alongside passionate coworkers, all the while making a rewarding impact and Keeping Commerce Human. We believe exceptional companies are built by exceptional teams, and we're intentional about it. That means hiring great people, setting them up for success from day one, and giving them real reasons to grow their careers here. We invest in development that goes beyond promotions, and we foster the trust and relationships that help people do their best work together. What’s the role? We are looking for a Senior Software Engineer I, Machine Learning to join the Search Systems team at Etsy. This team owns the core retrieval and indexing infrastructure that powers fast, reliable, and seamless search experiences for millions of Etsy buyers. As we embark on a major next-gen infra upgrade, the team has been focused on consolidating our retrieval systems, simplifying our architecture, and unlocking new machine learning capabilities to improve relevance, performance, and developer experience. This is a full time role reporting to the Engineering Manager. What’s this team like at Etsy? The Search Systems team is part of the Search organization and provides the foundational technology that enables high-quality search at scale. Our mission is to ensure Etsy’s search stack is fast, reliable, and extensible—serving hundreds of millions of listings efficiently while supporting rapid ML experimentation and innovation. This team is responsible for: Owning and operating next-gen retrieval infra and other search backends that power Etsy’s core retrieval layer. Unify our retrieval infrastructure (lexical and ANN infra) across Etsy products, simplify system architecture, and enable ML-based rankers in retrieval. Building and maintaining scalable, low-latency systems that meet strict SLAs and power live A/B experiments. Collaborating closely with applied scientists, Data Platform, ML Enablement teams, and product engineers to integrate new retrieval models and unlock advanced ranking capabilities. Utilizing numerous AI tools to unlock both individual and team velocity, developing agentic workflows while improving developer experience. What does the day-to-day look like? Design, build, and maintain search backend systems and infrastructure. Partner with ML modeling teams to productionalize new retrieval and ranking models efficiently at scale. Ensure reliable data pipelines, index health, and performance. Develop features around indexing, query execution, and ranking infrastructure to improve latency, throughput, and system resilience. Collaborate with cross-functional partners across other Search ML and Enablement Teams. Contribute to a culture of technical excellence, mentorship, and continuous learning through regular code reviews, design discussions, and performance feedback. Of course, this is just a sample of the kinds of work this role will require! You should assume that your role will encompass other tasks, too, and that your job duties and responsibilities may change from time to time at Etsy's discretion, or otherwise applicable with local law. Qualities that will help you thrive in this role are: You build and ship production ML systems, ideally in real-time search, recommendation, or ads systems. You have strong engineering and coding skills, with the ability to write high quality production code. Proficiency in Python, Scala, Java and/or other equivalent languages. You have experience with system performance optimization, caching strategies, and scaling high-throughput, low-latency services. You turn ideas into deeply reliable and well tested code that other people – or you, six months into the future – will find easy to comprehend and modify