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 job
We 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 do
- Feature 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 widgets
- Latency 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 users
- Prompt 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 quality
- Experimentation: help enable A/B testing for model and prompt changes, using evaluation gates to ship safely and measure impact
- Data and evaluation: contribute to synthetic Q&A generation, golden test sets, and evaluation dataset design that supports the features you’re building
- Infrastructure: contribute to Databricks, AWS (EKS), Terraform, or CI/CD work as initiatives require it
- Cross-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 features
Experience and skills
Must have:
- 7+ years of software engineering, with recent hands-on experience building product features backed by LLMs
- experience with at least one of: prompt engineering, LLM evaluation, fine-tuning, or model serving
- strong Python, and comfort working with APIs/SDKs that wrap LLM calls, prompt templates, and structured outputs
- product sensibility: a track record of shipping user-facing features, with attention to latency, tone, and quality of AI output as experienced by end users
- comfort picking up new infrastructure tools (Databricks, AWS, Terraform, GitHub Actions) as needed — deep prior expertise not required
Nice 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 experience
- data engineering fundamentals (Spark, Delta tables, Parquet)
#LI-KP1 #LI-Hybrid
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
- In-person collaboration and work in a hybrid model, with 3 days per week spent in the office
- 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.
Skills Required
- 4+ years of professional experience in machine learning
- Hands-on experience building and deploying production-grade AI/ML systems
- Engineering experience with LLM infrastructure and tooling including fine-tuning
- Strong Python programming skills for model development
- Experience with modern ML infrastructure tools
- Databricks platform experience for end-to-end AI/ML workflows
- Cloud platform expertise with AWS, GCP, or Azure
- Understanding of the entire ML/LLM development lifecycle
- Ability to devise creative solutions to technical challenges
- Excellent communication skills
Flo Health Inc. Compensation & Benefits Highlights
The following summarizes recurring compensation and benefits themes identified from responses generated by popular LLMs to common candidate questions about Flo Health Inc. and has not been reviewed or approved by Flo Health Inc..
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Parental & Family Support — Offerings include fully paid parental leave with additional support such as a return‑to‑work bonus and a dedicated policy for pregnancy loss. Coverage explicitly extends to adoptive and same‑sex parents, signaling inclusive family support.
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Leave & Time Off Breadth — Paid holiday and fully paid sick leave allocations are presented as substantial on top of local public holidays. This breadth indicates strong time‑off support relative to common market practices.
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Equity Value & Accessibility — Company‑wide eligibility for an employee share plan is highlighted as part of total rewards. Accessible equity participation can meaningfully augment overall compensation value.
Flo Health Inc. Insights
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. --------------- Flo in numbers: --------------- #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.
