Software Development Engineer - Full Stack, Ads

As a Junior Software Development Engineer - Full Stack on the Advertising team, you will help build and maintain backend services and APIs that support our advertising platform. While your primary focus will be backend development, you will also work across the full stack when needed—touching front-end components and collaborating with cross-functional teams to deliver features end to end. You’ll write clean, maintainable, and well-tested code, contribute to technical decisions, and support product rollouts with an eye on operational excellence and metrics. Design, develop, and deploy scalable backend services and APIs that power advertising experiences on OfferUp. Collaborate with product managers, business analysts, and peer engineers to design, implement and deliver new features. Contribute to front-end development (e.g., React Native) as needed. Maintain and improve existing codebases across backend and frontend systems. Participate in code reviews and contribute to technical design discussions. Help ensure high quality and operational excellence through testing, monitoring, and debugging.