Senior Site Reliability Engineer - Edge in London

In the dynamic landscape of On, our technology thrives much like a spirited runner: always moving, always improving. We are building the foundation that allows our engineering organization to scale, innovate, and deliver "Wow" to athletes worldwide. To power this mission, we are seeking a Senior Site Reliability Engineer (SRE) - Edge who understands that reliability, security, and performance start at the transport layer.

You won’t just manage a CDN; you will own the architecture and performance of our global entry points, including our Apollo GraphQL API Gateway. You will leverage expert-level knowledge of HTTP/S, TCP, and DNS to optimize for global throughput. This is a hands-on senior role where you will troubleshoot advanced network bottlenecks, design our future content delivery strategy, and act as the technical authority for our Web Application Firewall (WAF), bot mitigation, and standardized service authentication.

Your Mission

• Edge Architecture & API Gateway: Ensure high availability (99.95%+ uptime) for On’s digital platforms and our central Apollo GraphQL Gateway. You will design the "front door" of our infrastructure to be elastic, handling the unique scaling demands of both static web assets and complex federated API traffic.
• Traffic Engineering & Segmentation: Lead the strategic roadmap for our CDN (Cloudflare) and networking stack. You will distinguish between the needs of customer-facing web applications and internal service-to-service communication, implementing optimized routing for each.
• Environment Isolation & Security: Implement and maintain robust guardrails to protect our internal ecosystem. You will be responsible for restricting pre-production environments (e.g., Staging, QA) from the public internet using Zero Trust models, IP-based access controls, or OIDC-integrated tunnels.
• Standardized Auth & Access: Drive the standardization of authentication and authorization at the edge. You will ensure that every request entering our network is consistently validated, providing a secure and seamless identity layer for all microservices.
• Advanced Troubleshooting: Serve as the organization's "Level 3" expert for complex network traffic analysis. You are the one who dives into packet captures, TLS handshakes, and Apollo query latencies to find the root cause of global performance regressions.
• Shielding the Origin: Take full ownership of our WAF and Bot Management strategy. You will design and implement measures to protect our services from DDoS attacks and malicious actors without impacting the legitimate athlete experience.
• Infrastructure as Code (IaC): Treat the network and the gateway as code. You will manage edge configurations and gateway routing using Terraform, ensuring our security rules and routing logic are versioned, tested, and automated.

Your story

• Networking & Gateway Authority: You have a deep understanding of the OSI model and experience managing API Gateways (specifically Apollo GraphQL). You understand how to optimize the "supergraph" for performance at the edge.
• Edge & Security Specialist: Proven experience managing high-traffic CDN architectures (Cloudflare preferred) and a strong grasp of modern security protocols like OIDC, OAuth2, and JWT for standardizing service access.
• Infrastructure Security: You have experience implementing "Zero Trust" architectures and managing private network connectivity to isolate internal environments from public exposure.
• Cloud Native: You are comfortable in modern cloud environments (GCP/AWS) and have experience with Kubernetes (GKE), service mesh networking, and ingress controllers.
• Automation First: You believe that manual changes are technical debt. You are proficient in Terraform and familiar with CI/CD workflows (GitHub Actions) for deploying networking changes safely.
• Collaborative Leader: You enjoy working across teams (Security, DevEx, and Product) to solve horizontal problems. You can translate complex networking and auth concepts into actionable insights for non-experts.

About the Team

You will be joining the Platform Foundations group, a high-impact collective of engineers dedicated to building the "Engine" of On's technology. We manage our cloud infrastructure, Developer Experience (DevEx), and the Edge. We are a global team that values a "lead-by-example" culture. You will work alongside Staff and Principal engineers to bridge the gap between infrastructure and product, ensuring our technical investments directly accelerate the velocity of On’s mission.

On is a place that is centered around growth and progress. We offer an environment designed to give people the tools to develop holistically – to stay active, to learn, explore and innovate. Our distinctive approach combines a supportive, team-oriented atmosphere, with access to personal self-care for both physical and mental well-being, so each person is led by purpose.

On is an Equal Opportunity Employer. We are committed to creating a work environment that is fair and inclusive, where all decisions related to recruitment, advancement, and retention are free of discrimination.

We want to set everyone up for success, so here’s the lowdown on how we hire. Our process is a two-way street – bringing you into our culture, while helping us learn how you think. Our full process can last about eight weeks from application to offer, because we care about getting it right. These steps explain how we usually do things.

Before you get started, feel free to consider if you want to work with us. Strange question? Well, we give people a lot of space to navigate their day-to-day and that style isn’t for everyone. We want you to be passionate about what you do and be sure this is the right fit. Because when skills and passion combine – it creates that 'Wow' moment.

Step One: It starts with you... You’ll start by submitting your application to a specific role. We try to keep this step as simple as possible. We do get a lot of applications, but we review them all. If you’re a good fit to the role, a recruiter will follow up with you directly. If you didn’t receive a reply, or were unsuccessful this time around, we encourage you to look for other possible matches at On.