Senior Software Engineer II, Backend

About Poshmark Poshmark is the leading fashion marketplace where style comes alive through discovery, self-expression, and human connection. Powered by a vibrant community of 165 million members, Poshmark brings real people and taste to shopping through a social experience shaped by shared discovery. Buying and selling fashion feels simple, joyful, and personal, while every item tells its own story. Poshmark empowers sellers to grow meaningful businesses, keeps fashion in circulation longer, and gives shoppers access to unique and trusted finds, from everyday pieces to one-of-a-kind vintage and luxury. Poshmark is looking for a Senior Software Engineer II to join our Core Platform team and build reliable, scalable, and high-performance backend systems that power our marketplace. In this role, you will independently own complex backend features and services from technical design through production. You will solve challenging engineering problems across distributed systems, make thoughtful technical trade-offs, and work closely with Product, QA, Infrastructure, and other engineering teams. You will also contribute to technical design discussions, mentor junior engineers, and help improve the reliability, maintainability, and operational excellence of the systems owned by the team. Responsibilities Design, develop, test, deploy, and operate scalable backend services that support Poshmark’s marketplace.Independently own complex, well-defined technical initiatives from requirements and design through production rollout and ongoing support.Translate product and technical requirements into reliable, maintainable, and extensible software solutions.Make sound design and implementation decisions by evaluating scalability, performance, reliability, security, and operational trade-offs.Develop and enhance APIs, data models, asynchronous workflows, and integrations across distributed systems.Troubleshoot complex production issues, perform root-cause analysis, and implement sustainable fixes.Improve system observability, monitoring, performance, fault tolerance, and operational readiness.Participate actively in technical design reviews and provide constructive feedback through code reviews.Collaborate with Product, QA, Infrastructure, and adjacent engineering teams to manage dependencies and deliver high-quality solutions.Contribute to improving development processes, engineering practices, tooling, and team workflows.Mentor junior engineers and support their technical development through design discussions, code reviews, and knowledge sharing.Participate in production support and on-call responsibilities as required by the team. What You Will Accomplish In The First 6 Months Develop a strong working knowledge of Poshmark’s architecture, technology stack, development practices, and production environment.Independently deliver a complex backend feature or service from technical design through production.Take ownership of the quality, reliability, and operational health of assigned services or components.Contribute meaningfully to technical design discussions and code reviews.Build effective working relationships with Product, QA, Infrastructure, and adjacent engineering teams.Identify and implement improvements to the performance, reliability, maintainability, or developer experience of an owned system. What You Will Accomplish in 12+ Months Consistently lead the end-to-end delivery of complex backend initiatives within the team’s scope.Become a trusted technical owner for one or more important services or components.Drive measurable improvements in system scalability, performance, reliability, or operational efficiency.Help scope technical work, identify dependencies, and manage delivery risks for team initiatives.Contribute recommendations to the team’s architectural direction and technical roadmap.Strengthen engineering practices through design reviews, code quality improvements, documentation, testing, and operational standards.Mentor junior engineers, interns, and new team members and help them become productive within the organization.Share technical knowledge and lessons learned across the team. Requirements Bachelor’s or Master’s degree in Computer Science, Engineering, or a related technical discipline, or equivalent practical experience.7+ years of professional software engineering experience, including experience building and operating production backend systems.Strong foundation in computer science fundamentals, including data structures, algorithms, object-oriented design, and software design principles.Proficiency in at least one backend programming language such as Ruby, JRuby, Java, or a comparable language.Experience designing, developing, and maintaining APIs and backend services.Experience working with distributed systems and understanding their scalability, reliability, and performance considerations.Experience with databases, data modelling, caching, search technologies, or messaging systems.Experience writing clean, maintainable, well-tested, and well-documented production code.Strong debugging and problem-solving skills, including experience diagnosing issues in production environments.Understanding of monitoring, observability, automated testing, deployment, and operational readiness.Ability to independently drive technical work while collaborating effectively with engineers and cross-functional partners.Strong written and verbal communication skills, with the ability to explain technical decisions and trade-offs clearly.Demonstrated commitment to product quality, customer experience, and continuous improvement. Preferred Qualifications Experience with Amazon Web Services or another major cloud computing platform.Experience with one or more of the following technologies: Ruby, JRuby, Java, MongoDB, Elasticsearch, RabbitMQ, and Linux.Experience building cloud-native services for a high-traffic consumer or marketplace platform.Experience with service-oriented or microservices-based architectures.Experience with performance optimization, capacity planning, and production incident response.Experience with email, push notification, or other large-scale messaging technologies.Previous experience mentoring junior engineers, interns, or new team members.