Senior Full Stack Engineer

About ThredUp
ThredUp is transforming resale with technology and a mission to inspire the world to think secondhand first. By making it easy to buy and sell secondhand, ThredUp has become one of the world's largest online resale platforms for apparel, shoes and accessories. Sellers love ThredUp because we make it easy to clean out their closets and unlock value for themselves or for the charity of their choice while doing good for the planet. Buyers love shopping value, premium and luxury brands all in one place, at up to 90% off estimated retail price. Our proprietary operating platform is the foundation for our managed marketplace and consists of distributed processing infrastructure, proprietary software and systems and data science expertise. With ThredUp's Resale-as-a-Service, some of the world's leading brands and retailers are leveraging our platform to deliver customizable, scalable resale experiences to their customers. ThredUp has processed over 172 million unique secondhand items from 55,000 brands across 100 categories. By extending the life cycle of clothing, ThredUp is changing the way consumers shop and ushering in a more sustainable future for the fashion industry.

Recognized on TIME's Best Inventions 2024, TIME's Most Influential Companies of 2023, Digiday's WorkLife , TIME's Best Inventions of 2022, and Lattice's People Success Awards 2022.

*How You Will Make an Impact*
ThredUp is reshaping how the world thinks about secondhand fashion. As a Senior Full Stack Engineer (Core E-comm), you'll take ownership of the systems that power our buyer experience, from seamless onboarding to checkout and returns. At ThredUp's scale, your work won't just ship features; it will influence architecture, raise engineering standards, and directly impact millions of customers discovering sustainable fashion every day.

You'll work across our stack — from our Ruby on Rails monolith and adjacent microservices to our TypeScript/React-powered PWA — balancing improvements to mature systems with forward-thinking modernization efforts. You'll have the opportunity to drive long-term architectural enhancements in distributed systems, event-driven design, developer experience, and scalable frontend architecture.

In This Role, You Will

• Drive technical direction for core ecommerce services, balancing short-term delivery with long-term scalability.
• Take E2E ownership of critical flows, including purchasing, returns, promotions, and notifications.
• Collaborate with cross-functional partners to turn complex problems into simple, elegant solutions.
• Mentor engineers across teams, raising the bar for code quality, testing, and design practices.
• Lead system design discussions and contribute to architectural decisions.
• Experiment with AI-driven developer workflows to accelerate productivity and enhance platform intelligence.
• Own end-to-end initiatives, from architecture through monitoring and iterative improvements.

What We're Looking For

• 5+ years of professional software development experience, with strong proficiency in React, TypeScript, HTML/CSS, , and Ruby on Rails.
• Deep experience building and scaling APIs (REST and GraphQL) that power high-traffic, user-facing applications.
• Strong system design and debugging skills, able to reason across services, identify bottlenecks, and implement clean, maintainable solutions.
• UX empathy — you care about design details, accessibility, and crafting polished, intuitive user experiences.
• Solid database fundamentals (MySQL) and familiarity with background processing (Sidekiq, Redis) and asynchronous communication patterns.
• Performance-minded — you think about load times, bundle size, caching, and query optimization as part of the development process.
• Collaborative and ownership-driven with strong communication skills, comfortable partnering with product managers, designers, and other engineers to define and deliver impactful features.
• Curiosity and excitement about leveraging AI to accelerate web development (e.g., code generation, testing, performance optimization).
• JVM ecosystem experience (Java/Kotlin) is a plus.
• Experience scaling e-commerce or consumer apps with millions of users is a plus.
• Experience with MCP Servers and Agentic Commerce is a plus.

This role is not eligible for visa sponsorship.

What We Offer

• 4-day work week, with Fridays off
• Hybrid work environment: 3 days in the office and 1 day remote each week
• Competitive salary (we leverage market data)
• Many ThredUp employees also have the opportunity to own shares of ThredUp stock and are eligible for discretionary restricted stock unit awards
• Employee stock purchase plan
• Flexible PTO (take the time you need) + 13 company holidays
• Paid Sabbatical after 3 years of full time employment
• Generous paid parental leave for new mothers and fathers
• Medical, dental, vision, 401k, life and disability insurance offered
• We live by our Core Values of Transparency, SpeakingUP, Thinking Big, Infinite Learning, Influencing Outcomes & Seeking the Truth

*We believe diversity, inclusion and belonging is key for our team*
At ThredUp, our mission has been built on extending the lives of millions of unique clothing items. Much like our inventory, we are proud to have fostered a workplace that is one-of-a-kind. As a company focused on diversity, inclusion and belonging, we are committed to ensuring our employees are comfortable bringing their authentic selves to work every day. A unique perspective is critical to solving complex problems and inspiring a new generation to think secondhand first. Be you.

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the specific details of your disability related accommodation request. This email address is reserved for candidates with disabilities only. General application inquiries will not receive a response.