Senior Backend Engineer

<div class="content-intro"><p><strong>500M+ downloads. 80M+ monthly users. A decade of building – and we’re still accelerating.</strong></p> <p>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.</p> <p>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.</p> <p><strong>The job</strong></p></div><div> <p>Build systems that power the #1 Health App for Women</p> <p>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.</p> <p>At Flo, backend engineering is core product work.</p> <p><strong>We build:</strong></p> <ul> <li>Data-driven health insights that genuinely change lives</li> <li>Distributed systems that stay fast, available and scalable under massive real-time demand</li> <li>Privacy-first features like Anonymous Mode -  recognised in TIME’s Best Inventions</li> <li>Tooling and platforms that help Flo’s teams move faster, with fewer bottlenecks</li> </ul> <p>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.</p> </div> <div> <p style="line-height: 1.2;"><strong>Your Experience</strong></p> <p style="line-height: 1;"><strong><span style="font-size: 12pt;">You’ll thrive here if you:</span></strong></p> </div> <ul> <li>Have 7+ years’ experience building distributed backend systems</li> <li>Know what it takes to make systems fast, reliable and secure and when to prioritise each</li> <li>Are fluent in Java, Scala, Python or similar (and curious enough to learn Scala with us)</li> <li>Get DevOps, databases (SQL and NoSQL) and love designing APIs that just work</li> <li>Have a strong handle on writing clean, documented, version-controlled code</li> <li>Take ownership, show initiative and don’t wait to be told</li> <li>Are product-minded and always