Senior/Lead Backend Engineer

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

Build systems that power the #1 Health App for Women

We’re not a startup guessing what might work anymore, we’re operating at serious scale. Flo is used by 1 in 4 women aged 18–44 in the US. And we just hit our biggest month ever with 8.6M installs and a 2.8M MAU jump. The engineering behind that? Complex, distributed, secure and yours to help shape.

At Flo, backend engineering is core product work.

• Have 7+ years’ experience building distributed backend systems
• Know what it takes to make systems fast, reliable and secure and when to prioritise each
• Are fluent in Java, Scala, Python or similar (and curious enough to learn Scala with us)
• Get DevOps, databases (SQL and NoSQL) and love designing APIs that just work
• Have a strong handle on writing clean, documented, version-controlled code
• Take ownership, show initiative and don’t wait to be told
• Are product-minded and always thinking about the end-user impact

• Stream processing
• Public cloud infrastructure (AWS, GCP etc.)

What’s in it for you?

You’ll join a senior engineering team that moves fast, thinks big and builds tech used by millions daily. You’ll work on meaningful problems with real impact - in health, privacy and scale. This isn’t just code for the sake of code. This is building the future of personalised health.

#LI-Hybrid #LI-LM12

Salary Range – gross per month (ranges may vary based on skills and experience)

€6.500—€10.000 EUR

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

• Data-driven health insights that genuinely change lives
• Distributed systems that stay fast, available and scalable under massive real-time demand
• Privacy-first features like Anonymous Mode - recognised in TIME’s Best Inventions
• Tooling and platforms that help Flo’s teams move faster, with fewer bottlenecks

We’re tech-agnostic when hiring for backend. If you’ve built and run distributed systems and want to work in Scala (or already do), great. We’ll support your ramp-up. What matters most: you can solve problems, own outcomes, and keep learning.

Your Experience