500M+ downloads. 80M+ monthly users. A decade of building - and we’re still accelerating.Flo is the world’s #1 health & fitness app worldwide on a mission to build a better future for female health. Backed by a $200M investment led by General Atlantic, we became the first product of our kind to reach a $1B valuation in 2024 - and we’re not slowing down.With 7M paid subscribers and the highest-rated experience in the App Store’s health category, we’ve spent 10 years earning trust at scale. Now, we’re building the next generation of digital health - AI-powered, privacy-first, clinically backed - to help our users know their body better.The jobWe are looking for a Senior AI Engineer with strong LLM and product engineering experience to join our AI Platform team and help ship the AI-driven features across our app — including personalized in-app content recommendations, conversational AI-powered insights, and AI-generated mobile push notifications. You will focus on the product-facing behavior of our GenAI features (relevance, quality, latency, and safety), using the platform’s judges, fine-tuning pipelines, and evaluation tools, and contributing to infrastructure work (Databricks, AWS, Terraform) as initiatives require it.What you’ll doFeature development: build and ship LLM-powered product features, including AI-generated mobile push notifications, personalized in-app content recommendations and custom user journeys, and conversational AI-powered insights — including structured output such as charts and widgetsLatency and UX: reduce perceived and actual response latency through streaming, pregeneration, and inference-time tradeoffs, working closely with product and design on how AI output is experienced by usersPrompt and model behavior: iterate on prompt design and calibration, use fine-tuned health-domain models (Llama, Gemma, MedGemma) where relevant, and work with the Judge-as-a-Service ecosystem to keep outputs safe and high qualityExperimentation: help enable A/B testing for model and prompt changes, using evaluation gates to ship safely and measure impactData and evaluation: contribute to synthetic Q&A generation, golden test sets, and evaluation dataset design that supports the features you’re buildingInfrastructure: contribute to Databricks, AWS (EKS), Terraform, or CI/CD work as initiatives require itCross-functional impact: collaborate with Product, Security, Analytics, and Medical teams, and engage with technology partners (Databricks, Google, OpenAI, Anthropic, AWS) on pre-release capabilities relevant to your featuresExperience and skillsMust have:7+ years of software engineering, with recent hands-on experience building product features backed by LLMsexperience with at least one of: prompt engineering, LLM evaluation, fine-tuning, or model servingstrong Python, and comfort working with APIs/SDKs that wrap LLM calls, prompt templates, and structured outputsproduct sensibility: a track record of shipping user-facing features, with attention to latency, tone, and quality of AI output as experienced by end userscomfort picking up new infrastructure tools (Databricks, AWS, Terraform, GitHub Actions) as needed — deep prior expertise not requiredNice to have:LLM evaluation frameworks (judges, graders, calibration methodology) or fine-tuning techniques (LoRA, RLHF/DPO, model distillation)prompt optimisation frameworks (DSPy or similar)feature stores or personalization/ranking experience (relevant to in-app content recommendation work)healthcare, regulated-industry, or safety-critical AI systems experiencedata engineering fundamentals (Spark, Delta tables, Parquet)#LI-KP1 #LI-Hybrid Annual Salary Range (ranges may vary based on skills and experience)120,000—150,000 GBPHow we workWe’re a mission-led, product-driven team. We move fast, stay focused and take ownership - from brief to build to impact. Debate is encouraged. Decisions are shared. We care about craft, ship with purpose, and always raise the bar.You’ll be working with people who take their work seriously, not themselves. It takes commitment, resilience, and the drive to keep going when things get tough. Because better health outcomes are worth it. What you'll getWe support impact with meaningful reward. Here’s what that looks like:Competitive salary and annual reviewsOpportunity to participate in Flo’s performance incentive schemePaid holiday, sick leave, and female health leaveEnhanced parental leave and pay for maternity, paternity, same-sex and adoptive parentsAccelerated professional growth through world-changing work and learning supportIn-person collaboration and work in a hybrid model, with 3 days per week spent in the office5-week fully paid sabbatical at 5-year FloversaryFlo Premium for friends & family, plus more health, pension and wellbeing perksDiversity, equity and inclusionOur strength is in our differences. At Flo, hiring is based on merit, skill and what you bring to the role - nothing else. We’re proud to be an equal opportunity employer, and we welcome applicants from all backgrounds, communities and identities. Read our privacy notice for job applicants.
Senior ML/AI Engineer in London employer: Flo Health
Flo Health is an exceptional employer, offering a dynamic work culture in the heart of London where innovation thrives. As a Data Science Lead, you'll not only have the opportunity to shape cutting-edge ML models but also benefit from a collaborative environment that prioritises employee growth and development. With competitive compensation and a focus on work-life balance, Flo Health stands out as a place where your contributions directly impact user acquisition and marketing strategies.
