Senior Applied Scientist — Ranking & embeddings

Meridian Marketplace UK powers discovery for millions of buyers and sellers. Ranking blends classical signals with embeddings and fresh GenAI-assisted features—we need rigorous science and pragmatic experimentation.

Join our London hybrid office as a Senior Applied Scientist. You will collaborate with PMs, infra, and integrity teams to ship measurable relevance gains without compromising safety.

What you will do

• Design and analyse ranking / retrieval experiments: embeddings quality, calibration, exploration, and cannibalisation checks.
• Build offline metrics that correlate with marketplace KPIs; champion guardrails for cold-start and abusive patterns.
• Prototype new models (training and fine-tuning where justified) and coordinate production handoff with ML platform.
• Partner on A/B platform design: power analysis, ramp strategy, and automated monitoring for long-tail segments.
• Document methods and ship reusable datasets and feature libraries for the wider team.

What we look for

• MS/PhD in CS, stats, or related field—or equivalent industry track record in search / recommendations.
• Strong Python, SQL, and PyTorch (or similar); experience with large-scale feature stores and experimentation.
• Clear communication of causal and statistical nuance to product partners.
• 5+ years shipping ranking, search, or personalised feed systems at scale.
• Right to work in the UK.

Nice to have

• Exposure to two-sided marketplaces and fairness/safety constraints.
• Experience with Snowflake or BigQuery analytics loops.
• Publications or internal memos on embeddings or learning-to-rank.