Senior AI Engineer - Recommendation and Personalisation in London

About 9fin: 9fin is the AI platform powering global debt markets — the world’s largest asset class at over $145 trillion. Debt markets are vast, global, and mission-critical, yet still run on fragmented data, PDFs, and manual workflows. 9fin replaces this broken infrastructure with a single platform that centralises proprietary credit data, deep analysis, and high-value workflows across global markets. Today, 9fin powers teams at 300+ blue-chip institutions worldwide, including global banks, asset managers, private equity firms, law firms, and advisors. The business is scaling at exceptional speed, with rapid expansion in the US and best-in-class retention driven by deep workflow adoption.

The Opportunity: The Data Science team is growing at 9fin! We are doing world-class work with groundbreaking technologies to build data-driven products using machine learning, computer vision, natural language processing, speech and audio, and knowledge/data mining. We are looking for a Senior AI Engineer to accelerate our application of AI across teams and products. Come and join us, you will get to build large-scale AI powered systems, learn and apply the latest techniques, and work alongside other great researchers and engineers!

Every day is different, but here's an example of the kind of things you'll work on:

• Design and build generative AI applications tailored to complex financial and legal workflows, leveraging state-of-the-art models to deliver innovative, practical solutions that streamline decision-making and unlock new efficiencies.
• Drive end to end model development lifecycle, leading the team in best practices, ensuring reproducible research and well managed model delivery/deployment.
• Collaborate cross functionally to share diverse ideas, understand business problems, and elevate/mentor your teammates.
• Translate complex problems into well-defined scoped bets in an internal startup style environment, dynamic and fast-paced.
• Learn and apply ground-breaking research and approaches in advanced topics, iterating improvements with a fail fast mentality.
• Be a proactive sharer of compelling ideas/work to the rest of the team and organisation. We want you to help lead/push the adoption of AI throughout 9fin.

What Makes This Role Different: This role is focused on deciding what information each user should see, in what order, and at what moment. While experience with retrieval systems, knowledge graphs, and LLMs is valuable, the core challenge is learning from user behaviour, workflow context, and content signals to optimise discovery, prioritisation, and decision-making across feeds, alerts, search, and AI experiences.

About You: This role will be a great fit if you have:

• Deep experience building recommendation systems across feeds, alerts, search, and workflow products.
• Strong understanding of candidate generation, personalisation, ranking, and next-best-action systems.
• Learning to Rank: Expertise with pointwise, pairwise, and listwise ranking approaches, including reranking, diversity, freshness, novelty, deduplication, and relevance optimisation.
• User Modelling & Behavioural ML: Experience modelling user intent, preferences, workflows, and engagement patterns. Familiarity with session-based learning, sequence modelling, and balancing short-term versus long-term user interests.
• Product Analytics & Telemetry: Strong understanding of behavioural instrumentation, including impression logging, clicks, dwell time, follows, saves, alert interactions, and event design that supports robust learning systems.
• Experimentation & Evaluation: Experience designing and analysing A/B tests, defining success metrics, understanding selection bias, and evaluating ranking systems using both online and offline methodologies.
• Feature Engineering & Applied Machine Learning: Strong background in feature engineering, tabular machine learning, calibrated scoring systems, and production use of models such as gradient-boosted trees, logistic regression, and related approaches.
• Content-Aware Recommendation Systems: Experience combining embeddings, semantic similarity, collaborative signals, and content understanding to build recommendation systems that perform well in sparse and cold-start environments.
• Graph & Entity-Aware Ranking: Ability to incorporate relationships between companies, sponsors, lenders, law firms, instruments, documents, and events into ranking and recommendation decisions.
• Production ML Engineering: Experience building feature pipelines, online and batch inference systems, low-latency ranking services, experimentation platforms, and monitoring for production machine learning systems.
• Strong proficiency in Python for production ready delivery.
• A strong product focus with a desire to understand the end-to-end impact of your solutions for our end users.
• Good knowledge of AWS’s AI infrastructure.

Benefits: We’re a scaling start up, and we enjoy sharing our success. When the company succeeds, we always reinvest that in our people. We also offer huge amounts of responsibility, an abundance of opportunity for growth and a platform to truly excel.

• Competitive Salary (our salary bands are benchmarked at the top end of the market)
• Equity
• Pension (your minimum contributions are 4% with 9fin matching up to 7%)
• Private Medical Insurance
• Paid sick leave with Income Protection for long periods of illness
• Group Life Assurance
• Season Ticket Loan & Cycle to Work schemes
• 25 holiday days per year
• Local public holidays (with the ability to exchange them for alternative days)
• Hybrid working model, to allow you the flexibility to decide how, where and when you do your best work
• Work abroad for up to 3 months a year
• 1 month paid sabbatical after 5 years of service
• Enhanced parental leave & flexible working arrangements available

Training & Culture: Professional learning and development budget, AI experimentation budget of £800 (UK) per employee to trial AI tools, quarterly team socials, summer and winter company social events.

9fin is an equal opportunities employer. At 9fin we are dedicated to building and promoting a fair and inclusive workplace where everyone can reach their full potential and truly belong. We recognise that building diverse teams enables a more creative and productive environment. If you’re excited about this role but your experience doesn’t perfectly align with the job description, we encourage you to apply anyway. You might just be who we’re looking for — either for this role, or perhaps another.