Staff ML Engineer - Trust & Safety

WHY THIS ROLE

AVIV Group runs some of Europe's best-known real estate platforms, and every one of them depends on trust: people need to find a home or a tenant, not a scam or a dead listing. Trust & Safety exists to protect that experience, and our north star is the share of leads that flow from good visitors to good listings. We are hiring a Machine Learning Engineer to build the systems behind it, from identity risk scoring to fraud-ring detection and listing integrity. This is an opportunity to build and improve, not simply maintain: the ML platform is still taking shape, so you will help define the ground you stand on.

THE TEAM YOU'LL JOIN

You'll join our Trust & Safety team, a group of around twenty people made up of data and backend engineers, data scientists and analysts, product managers and engineering managers. You'll work across immowelt, SeLoger and Immoweb and partner closely with Product, Policy and our human moderation operations. Our next chapter is about building ML-driven detection that replaces static rules, and turning integrity and reputation scores into inputs for search ranking and recommendations. This role will be central to making that happen.

WHAT YOU'LL OWN

• Models across the trust stack: Design, train and ship identity risk scoring, fraud and fraud-ring detection, listing integrity scoring, duplicate and republication detection, and behavioral signals on both sides of the marketplace.
• Adversarial resilience and error balance: Build models and retraining loops that hold up as bad actors adapt, catch bad listings before they are reported, and treat false positives as seriously as false negatives, because a false positive is an honest owner who can't publish their home.
• Evaluation you can trust: Run careful experiments that account for adversarial drift and feedback loops, where enforcement changes tomorrow's training data, and give an honest analysis when offline and online results disagree.
• The human moderation loop: Connect reviewer decisions to model training and route uncertain cases to reviewers, integrating with moderation tooling such as Implio and measuring the whole loop.
• Signals other teams build on: Ship integrity and reputation scores that are planned inputs to search ranking and recommendations.
• Production and foundations: Own serving, monitoring, SLOs and a share of on-call for what you ship, build the pipelines and evaluation setup the team needs while the group ML/AI platform matures, and strengthen the team through design reviews, mentorship and writing that makes good decisions repeatable.

WHAT WE'LL ACHIEVE TOGETHER

Success in this role means creating measurable improvements, not simply shipping more models. We expect you to help us:

• Increase the share of leads flowing from good visitors to good listings.
• Raise the share of bad listings caught before they are reported.
• Reduce false positives.
• Reduce the share of bad experiences users encounter year over year. The exact measures will be agreed based on the priorities and baseline when you join.

WHAT YOU BRING

We care more about what you have built and improved than a particular title or number of years of experience. The level we hire at, Senior or Staff, depends on your experience and the scope you're ready to take on. You bring:

• Experience shipping at least 3 ML systems to production at meaningful scale, typically with around 6+ years of engineering experience for Senior and 8+ for Staff.
• Hands-on experience in an adversarial or integrity domain such as fraud detection, anti-abuse, spam, content moderation, risk scoring or account security.
• A solid grounding in imbalanced, high-stakes classification: precision/recall trade-offs with real cost on both sides, threshold and policy design, and calibration.
• Experience evaluating models in feedback-loop systems, understanding how enforcement actions distort future training data and having worked around it in practice.
• Strong engineering fundamentals: production-quality code, reliable data pipelines and reproducible work.
• Technical influence beyond your own output, plus clear communication about uncertainty with engineers, policy and operations partners, and leadership, including when the honest answer is "we don't know yet." Nice to have: graph-based detection (fraud rings, identity graphs, device and payment linkage); LLM-based approaches to trust work (content understanding for moderation, scam-pattern detection, LLM-assisted review); experience alongside human review operations (uncertainty-based routing, active learning from moderation queues); a marketplace or classifieds background; familiarity with EU platform regulation such as the DSA.

HOW WE WORK AT AVIV

Our Leadership Behaviours describe not only what we expect people to deliver, but how we expect them to deliver it. For this role, four behaviours will be particularly important: All Starts With Me. You own what you ship end to end, including serving, monitoring and on-call, and when a model isn't holding up in production you understand why and drive it to resolution. Data Leads. Judgment Wins. You distinguish real signal from offline-metric comfort, are honest when offline and online results disagree, and combine data with judgment on thresholds and policy. Live for the Customer. You remember that a false positive is an honest owner who can't publish their home, and that a missed scam is a home seeker at risk, and you design with both people in mind. Simplify to Scale. You build pipelines, evaluation setups and signals that other teams can adopt, rather than one-off fixes.

WHAT TO EXPECT FROM THE HIRING PROCESS

We want our hiring process to be focused, transparent and respectful of your time. You can typically expect 3 interviews with the people you would work most closely with. Depending on the role, we may also include a technical assessment relevant to the work you would be doing, such as a coding or system design session. We'll explain the process from the start and keep you informed throughout.

ABOUT AVIV GROUP

Join one of the world’s largest and most innovative digital real estate tech companies. Backed by global investment leaders KKR and CPP Investments, AVIV Group is reshaping the way people across Europe buy, sell, rent, lease, and value real estate. With a strong presence in Europe, we power some of the region’s most recognized digital real estate platforms across various countries – including Immoweb, SeLoger, and Meilleurs Agents (France’s leading real estate valuation platform), alongside immowelt and Homeday (one of Germany’s fastest-growing PropTech companies). Our European footprint is complemented by our dynamic tech and engineering hubs in Romania and Croatia. Our mission? We simplify life’s most important transactions. By combining data, technology, and human expertise, we empower millions of people to find their perfect home! Help us shape the future of real estate.