500M+ downloads. 77M+ 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 6M 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 job
We're not chasing a product – market fit. We've found it. Flo is used by 1 in 4 women aged 18–44 in the US. Last year, $200M raised. Earlier this year: 8.6M new installs, 2.8M user jump. That kind of scale doesn't just happen. It's engineered – and increasingly, it's predicted.
That's where you come in.
We're hiring a Data Science Lead in London to build and lead our Predictive Growth Optimisation team – pioneering ML models that power our user acquisition strategy, predict lifetime value, and optimise our $25M+ annual marketing spend across channels.
This role owns the strategy, development, and continuous improvement of Flo's pLTV system - a mission-critical model reused across UA, AdTech, personalization, and financial forecasting. You'll balance hands-on technical leadership with people management, building production systems that directly impact our growth trajectory.
What you'll do- Lead & develop a team of 4+ ML and Backend engineers - hiring, mentoring, and setting technical direction
- Own pLTV strategy - architect and evolve our core predictive lifetime value models that inform millions in UA decisions
- Build production ML systems - from MMM algorithms to real-time forecasting models handling millions of daily predictions
- Drive cross-functional impact - partner with Growth, Product, and Finance to translate business problems into ML solutions
- Shape technical architecture - guide MLOps infrastructure, monitoring, and rapid iteration cycles
- Stay hands-on - contribute to modeling, architecture decisions, and technical problem-solving as needed
Technical Leadership
- 7+ years applied ML experience building and deploying models in production
- 4+ years managing technical teams (ML engineers, data scientists, or similar)
- Expert knowledge of ML fundamentals: supervised/unsupervised learning, time series, causal inference
- Experience with modern ML frameworks (PyTorch, TensorFlow, scikit-learn, CatBoost)
Growth & Product Experience
- Experience with growth analytics, attribution modeling, or marketing effectiveness
- Understanding of user acquisition funnels and retention optimization
- Comfortable translating business requirements into technical roadmaps
- Strong communication skills - can explain complex models to executive stakeholders
Production ML Systems
- Experience deploying ML models at scale (millions+ predictions/day)
- Knowledge of MLOps practices: model versioning, monitoring, automated retraining
- Understanding of data engineering fundamentals and cloud platforms
- Experience with Marketing Mix Modeling, attribution, or ad tech
- Background in consumer tech, mobile apps, or health tech
- Knowledge of privacy-preserving ML techniques and A/B testing methodology
How we work
We’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 get
We support impact with meaningful reward. Here’s what that looks like:
- Competitive salary and annual reviews
- Opportunity to participate in Flo’s performance incentive scheme
- Paid holiday, sick leave, and female health leave
- Enhanced parental leave and pay for maternity, paternity, same-sex and adoptive parents
- Accelerated professional growth through world-changing work and learning support
- Flexible office + home working, up to 2 months a year working abroad
- 5-week fully paid sabbatical at 5-year Floversary
- Flo Premium for friends & family, plus more health, pension and wellbeing perks
Diversity, equity and inclusion
Our 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.
Top Skills
What We Do
Flo is the essential female health partner. We are building a better future for female health by helping women harness the power of their body signals.
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Flo in numbers:
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#1 period tracker in the USA by active audience
#1 most downloaded female health app worldwide
47 million monthly active users
240 million installs
28M women got pregnant while using Flo (the number indicates users who logged pregnancy in app during 2015-2022)
Flo prioritizes safety and keeps a sharp focus on being the most trusted digital source for women's health information.
Flo intensively uses Data Science and AI to deliver the most personalized content and services available.
Flo is currently available in 22 languages on iOS and Android. 55% of users are located in the US and Europe.
We are committed to putting privacy of our users first. Our users trust our technology to keep their sensitive information private and we are responsible for providing a safe and secure platform for them to use. We regularly carry out privacy assessments to monitor risks including data protection impact assessments and third-party risk assessments. In March 2022 Flo completed an external, independent privacy audit which confirmed there are no gaps or weaknesses in our privacy practices.
