Senior Software Development Engineer

About the role:

As a Senior Backend Engineer on the Core team, you will play a critical role in maintaining and evolving OfferUp’s client engineering platform and app ecosystem, as well as leading efforts to build systems that detect and prevent fraudulent behavior in our marketplace. You will ensure app stability, performance, and developer efficiency by tackling complex technical challenges, collaborating across teams, and driving innovation. The systems you build will help maintain our community guidelines and support our partner team’s growth and business strategies, focusing on key issues such as account takeovers, Phishing, Payment chargebacks, and Prohibited Items. As a backend developer, you will build highly scalable systems to detect and prevent fraud and continuously improve our engineering/operational excellence.

What You’ll Do

• Work collaboratively with cross-functional teams (risk analysts, data science, and operations) to design and implement new features
• Analyze the latest attacker techniques and apply solutions to detect them holistically and stop them proactively
• Drive engineering and operational excellence across the Core engineering team
• Collaborate with OfferUp-wide engineering teams to improve processes, surface common pain points, develop solutions, and evangelize best practices
• Identify when to replace and when to rebuild legacy systems
• Participate in reasonable on-call rotations with the rest of the team
• Support, mentor, and help other engineers on the team
• Develop highly scalable classifiers and tools leveraging machine learning, data regression, and rules-based models
• Ensure app stability by identifying and resolving crashes, freezes, and network errors across both React Native and native layers
• Develop reusable tools and frameworks to streamline development and improve the developer experience
• Mentor and guide junior engineers, fostering best practices for frontend and native development

You’ll thrive in this role if you have:

• 5+ years of professional software engineering experience, of which at least 3 were devoted to web services
• 2+ years of experience in real-time messaging systems
• Experience performing data analysis and translating the results into business recommendations
• Experience in working with data-driven applications at scale
• Strong coding skills in Java, Python, Scala, Golang, or any other modern programming language, coupled with strong knowledge in object-oriented design and microservices architecture
• BS or MS in Computer Science, Computer/Software Engineering, Information Systems/Technology, Information Science, or a related discipline

Helpful, but not required:

• Proficiency in native development languages: Swift/Objective-C (iOS) and Kotlin/Java (Android)
• Experience with Agile development methodologies
• Experience with load balancing and handling massive data traffic
• Experience writing code in Python and Java
• Experience with cloud infrastructure AWS