Senior Backend Engineer

About the position

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 50 2023, 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 Backend 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 within our Ruby monolith and adjacent microservices, 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, and service decomposition. 

Beyond technical execution, you’ll collaborate across product, design, and data science, ensuring engineering efforts align with both customer needs and business goals. This is an opportunity to shape the technical backbone of a company making fashion more sustainable at scale. You’ll join a team that values ownership, experimentation, and continuous improvement; and, you’ll see the direct impact of your work on millions of customers.

In This Role, You Will 

● Drive technical direction for core commerce services, balancing short-term delivery with long-term scalability. 

● Take ownership of critical back-end 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 deep expertise in Ruby on Rails and scaling monolithic applications, including decomposition into services. 

● Strong API design skills (REST + GraphQL) and experience supporting high-volume cross-service communication. 

● Proficiency in relational databases (MySQL), event-driven systems (Kafka), and background processing (Sidekiq, Redis).

● Experience with containerized deployments (Docker, Kubernetes) and CI/CD workflows. ● Strong communication skills with a track record of driving technical decisions and writing clear documentation. 

● A proactive, ownership-driven mindset with comfort working in ambiguous, cross-functional environments. 

● Eagerness to learn new domains and contribute across the stack as needed. 

 ● JVM ecosystem experience (Java/Kotlin) a plus.

● Front-end or mobile exposure (PWA, iOS/Swift, Android/Kotlin) a plus. 

● Experience scaling e-commerce or consumer apps with millions of users a plus.

● Proven success leading initiatives, mentoring engineers, and shaping architecture a plus.

● Familiarity with performance monitoring and observability tools a plus.

● Strong product sense, specifically understanding how technical trade-offs affect UX and business outcomes 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.

If you are a candidate with a disability and have a reasonable accommodation request for the job application process, please email disabilitysupport@ThredUp.com 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.

Place of work