Principal Infrastructure Engineer

Description

The company has more than 500 million downloads and over 80 million monthly users, and has been building for about ten years.

It is ranked the number one health and fitness app in the world and aims to improve female health. A $200M investment led by General Atlantic brought its valuation to $1B in 2024, making it the first product of its kind to reach that level.

It has 7 million paid subscribers and the top-rated experience in the App Store's health category. It is building AI-powered, privacy-first, clinically backed digital health products.

More than 80 million women open the app each month. Every session runs on infrastructure the team builds, and the data involved is highly personal, so the work is keeping that infrastructure fast and private at this scale.

The Velocity team runs the platform all engineers build on: Kubernetes on AWS, the data stores behind the services, and standard paths that let product teams ship without deep infrastructure expertise. The team treats internal developers as its customers.

Responsibilities

• Design and run the Kubernetes and data infrastructure that supports 80 million monthly active users, aiming for stability that needs little attention.
• Turn your operational knowledge of clusters and databases into defaults that product teams get automatically.
• Architect and evolve the EKS environment, covering cluster lifecycle and upgrades, networking, autoscaling, workload isolation, and the Helm and Terraform used to deploy to it.
• Shape how services use PostgreSQL, DynamoDB and Kafka, setting common patterns for provisioning, access, backup, failover and capacity.
• Build self-service tooling and Terraform modules that give product teams autonomy while keeping systems stable and secure.
• Lead resilience work, including business continuity planning, disaster recovery testing and a sustainable on-call rotation.
• Support the infrastructure behind privacy features, including an anonymous mode recognised by TIME, and help maintain SOC 2, ISO 27001 and ISO 27701 certification while handling very sensitive data.
• Set up metrics, logs and traces so that problems are detected before users notice them.

Requirements

• Several years in infrastructure, platform, SRE or DevOps roles running high-traffic distributed systems in production.
• Experience at Principal or Staff level, setting direction across teams as well as delivering work.
• Hands-on experience running Kubernetes in production with real workloads, ideally on EKS. You can explain what happens between applying a manifest and a pod serving traffic, and you have debugged that path when it failed.
• Understanding of how PostgreSQL, DynamoDB and Kafka behave under load and when they fail, such as connection limits, replication lag, hot partitions, consumer lag and retention. You do not need to have been a DBA, but you know good practice and when to seek help.
• Strong AWS knowledge and fluent Terraform.
• Strong ideas about how infrastructure should support AI automation in development teams and the software delivery lifecycle, based on what you have seen of its impact.
• Written communication that favours documentation, and the ability to bring distributed product teams along with you.
• Bonus: experience with Go or Python coding.
• Bonus: experience hardening infrastructure for high-compliance or security-sensitive environments such as HIPAA, SOC 2 or PCI.
• Bonus: experience running managed data services on AWS (RDS, Aurora, MSK, DynamoDB) at scale, including migrations and major version upgrades.
• Bonus: experience scaling consumer platforms to millions of concurrent users.
• Bonus: certifications such as AWS Certified Solutions Architect Professional, CKA or CKS.

Conditions

The company is mission-led and product-driven, and moves quickly while keeping focus. Ownership runs from briefing through building to impact. Open debate is welcome, decisions are shared, and quality and standards are high.

You will work with people who are serious about their work without taking themselves too seriously. The role requires commitment, resilience and persistence through hard periods, in service of better health outcomes.

Salary range is £130,000 to £150,000 GBP per year, depending on skills and experience.

The role is hybrid, with 3 days per week in the office.

Annual reviews.

Benefits

• Participation 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.
• Support for professional growth, including learning support and work on high-impact problems.
• A fully paid 5-week sabbatical at the five-year anniversary.
• Premium access for friends and family, plus health, pension and wellbeing perks.