Senior DevEx Engineer in London

Overview

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 Scale of the Challenge

At Flo we don’t just have users, we have a global community. We are the #1 women’s health app, in the last month alone, we saw 8.6M new installs and a 2.8M increase in active users. This level of growth requires world-class engineering — increasingly augmented by AI, with engineers moving towards agentic development, where they design systems that collaborate with AI agents rather than writing everything manually.

The Mission: Velocity

The Velocity team exists to eliminate friction. We treat our internal developers as our customers. You will:

• Abstract Complexity: Build intuitive tooling that enables self-service allowing devs to focus on product logic.
• Standardize Excellence: Bake best-practices, security, observability, and scalability into the core stack so they aren't afterthoughts.

What You Will Do

• Developer Experience: Build self-service tools that give product teams autonomy without sacrificing system stability.
• Platform Engineering: Architect and evolve our core stack (AWS, EKS, Terraform).
• Systems Resilience: Lead reliability initiatives, including business continuity planning and a sustainable on-call rotation.
• High-Scale Privacy: Support the infrastructure for industry-leading privacy features, such as our TIME-recognized "Anonymous Mode."
• Observability: Implement best-in-class monitoring (metrics, logs, tracing) to ensure issues are identified and mitigated before they impact the user.

What You Bring

• Experience: 6+ years in Infrastructure, DevEx, SRE, or DevOps roles supporting high-traffic, distributed environments.
• Cloud Native Mastery: Deep expertise in AWS and Kubernetes (K8s) is essential.
• Automation Mindset: Proficient in Infrastructure as Code (Terraform) and Configuration Management.
• Technical Breadth: Ability to script and build tools in multiple languages (Python, Go, Scala, or Bash).
• Deep Systems Knowledge: You’re comfortable debugging at the Linux kernel level and analyzing performance via, for example, flame graphs.
• Communication: A "doc-first" mentality and the ability to collaborate across distributed product teams.

Bonus Points

• Background in hardening infrastructure for high-compliance or security-sensitive environments.
• Experience scaling consumer tech platforms with millions of concurrent users.
• Professional Accreditation such as AWS Professional Architect, CKAD or KCSA.

Why Join Flo?

• High Impact: Flo is re-writing women’s health.
• Autonomy: We hire experts and empower you to deliver.
• Cutting-Edge Stack: Work with modern tools like Sentry, EKS, and Terraform in a fast-paced, "fail-forward" environment at a huge scale.

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

• 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.