Senior Data Scientist, Decision Science (AI/ML)

Location: London, UK; hybrid working with 3 days a week in the office

Company

hirify.global operates lead-generation teams and AI and rule-based agents that diagnose performance issues and recommend marketing actions.

What you will do

• Build classification, ranking, anomaly-detection, and forecasting models for lead quality and traffic performance.
• Design validation, calibration, leakage checks, drift monitoring, and model evaluation with the platform team deploying models on SageMaker.
• Measure model impact against commercial KPIs, including A/B tests where randomisation is possible.
• Frame business decisions as actions, context, and rewards, using current rules as baselines.
• Develop contextual-bandit policies with safe exploration and learn from operator overrides.
• Define evidence, confidence thresholds, and guardrails for handing agent decisions over to autonomous operation.

Requirements

• 5+ years as a data scientist or in a similar applied ML role, including taking models to production and maintaining them.
• Statistics and experimentation skills covering hypothesis testing, A/B testing, power, and sample sizing.
• Classical ML experience with classification and ranking using scikit-learn and XGBoost or LightGBM, including rigorous validation design, calibration, and leakage prevention.
• Independent applied experience with at least one of contextual bandits, causal inference, or uplift modelling.
• Strong Python and SQL skills, plus Git and code review experience.

Nice to have

• Production experience with bandits, off-policy evaluation, or uplift modelling, including tools such as Vowpal Wabbit, Open Bandit Pipeline, EconML, or DoWhy.
• Time-series forecasting for budgets, pacing, or demand.
• Experience with Snowflake, dbt, or AWS SageMaker.
• Lead-generation or ad-tech experience.

Culture & Benefits

• Hybrid work with 3 office days per week; work from anywhere for 2 weeks per year.
• 25 days of paid holiday plus 8 bank holidays, increasing by 1 day per year up to 30 days; additional Christmas closure days.
• Summer Fridays, health, dental, and vision benefits allowance, life assurance, income protection, and defined-contribution pension with salary sacrifice.
• Paid maternity and paternity leave subject to qualifying conditions, including support for same-sex and adoptive parents.
• Wellbeing and mental-health programme, family support, and 2 charity days per year.
• Work is guided by commercial impact, ownership, candid communication, continuous improvement, technical mastery, and judgement under ambiguity.