Senior Backend Engineer, Trust & Safety

As a Senior Backend Engineer II in the Zen team, you will be responsible for building the systems that help keep counterfeit items off Vinted, while protecting legitimate sellers.

Zen sits in the Trust domain and owns the counterfeit detection problem end to end, not just the tools. We combine rules, machine learning and modern AI to find counterfeit listings, understand where detection falls short and keep improving it. The work has a direct impact on how safe and trustworthy Vinted is for our members, and we're growing our use of AI to make that protection work at Vinted's scale.

We work with Go, Ruby and Python, alongside ML models and LLMs.

In this position, you’ll

• Design and build the backend services behind counterfeit detection.
• Spot new counterfeiting patterns early and turn them into new detection capabilities.
• Take technical ownership of complex projects, from idea to production, including writing RFCs and making architecture decisions.
• Build AI-driven capabilities, including LLM-based systems, that are reliable, observable and cost-aware.
• Collaborate with data and decision scientists, using data to make decisions and bringing engineering input to how detection and models are improved.
• Measure the impact of what we ship, with accuracy and fairness to legitimate sellers in mind.
• Raise the bar for engineering and agentic development by mentoring engineers in the team and beyond.

• Proven experience designing, building and operating ML- and data-driven backend systems in production, with Go, Ruby or Python, including event-driven systems.
• Curiosity and drive to explore and apply AI to counterfeit detection, staying on top of the latest developments in LLMs and their practical applications.
• Solid understanding of data, ML and LLMs: how models are trained, evaluated and retrained, and how to build reliable systems around them.
• Comfortable working with data and decision scientists, using data to make decisions and contributing valuable engineering input.
• Demonstrated ability to own complex, ambiguous problems end to end and drive technical decisions.
• Pragmatic about trade-offs between catching abuse and protecting legitimate sellers, and able to explain technical decisions to non-engineers.

Nice to have

• Bonus: experience with BigQuery, Vespa, Temporal

• The opportunity to benefit from our share options programme
• 25 working days of holiday
• Access to all the tools & tech needed for work
• Home office support: we provide IT workstation equipment and a personal budget of up to 540 for home workplace furniture
• Private health insurance
• Pension plan with flexible contribution options and a matching contribution from Vinted
• Confidential Employee Assistance Program (EAP) for you and your family
• Frequent team-building events
• A personal monthly budget for shopping on Vinted
• A dog-friendly office
• In Vilnius office: Gym & in-house meals at friendly prices
• In Kaunas office: a monthly lunch allowance, and a once-a-week provided in-house lunch and breakfast