Senior Network Engineer in London

Company Overview

Radiant is redefining how AI infrastructure is built. We design and operate AI‑native cloud platforms engineered for sovereignty, performance, and scale. Our infrastructure powers GPU‑native workloads, multi‑tenant control planes, and high‑performance AI systems designed for the most demanding environments. We are not building a generic cloud. We are building purpose‑built AI infrastructure – from powered land, to compute, to software. As we scale our platform and expand our engineering organization, we are looking for leaders who can build strong teams, uphold high standards, and deliver reliably at pace.

Job Description

As a Senior Network Engineer, you’ll design, deploy, and operate the high‑performance, low‑latency network fabric that underpins our GPU infrastructure. You’ll play a critical role in shaping the architecture, automation, and operational standards of our network, ensuring it meets the rigorous demands of modern AI training and inference workloads. The ideal candidate is a strong advocate of engineering excellence and operational best practices. You’re customer‑focused, collaborative, and equally comfortable discussing technical issues with enterprise customers, internal teams, and cross‑functional stakeholders. You’ll contribute to everything from design and implementation through to L3/L4 operational support.

Role Responsibilities

• Network Architecture & Collaboration: Design scalable leaf‑spine networks using Mellanox switches with Cumulus Linux, integrated with Juniper PTX routers and SRX firewalls. Lead 3rd party and internal provider collaboration to deploy resilient site‑to‑site and internet connectivity, optimise topology, and resolve complex faults.
• Operations & Maintenance: Perform configuration, upgrades, and deep troubleshooting of Juniper and NVIDIA/Cumulus devices in production environments.
• Software‑Defined Networking (SDN): Implement programmable network designs using controller‑based platforms to support automation and scalability.
• Kubernetes Networking: Support networking within container platforms using CNIs such as Calico, Cilium, or Kube‑OVN. Understand microservices traffic patterns and service mesh integrations.
• Automation & Scripting: Develop and maintain Ansible playbooks and Python automation for configuration management, provisioning, and compliance, including working against API interfaces of network equipment.
• Monitoring & Telemetry: Implement observability tools using SNMP, sFlow, and gRPC to detect and address network bottlenecks at scale.
• Incident Management: Lead L3/L4 network incident response, escalation management and root cause analysis in high‑pressure, 24x7 production environments.
• Stakeholder & Customer Engagement: Act as a trusted technical expert, engaging directly with internal stakeholders and enterprise customers. Present solutions and troubleshoot effectively across all levels of the organisation.
• Engineering Excellence: Promote and uphold best practices in configuration management, change control, documentation, and continuous improvement.

Requirements

• HPC/AI Networking: 3–5 years’ experience supporting high‑throughput, low‑latency infrastructure for GPU‑based or HPC clusters.
• 8–12+ years in networking, often with at least 5 years in globally distributed environments.
• Experience with multi‑region or multi‑continent backbone networks, transit/peering, and high‑availability design at Internet scale.
• Hands‑on with large‑scale routing (BGP/MPLS), automation at scale, and often SDN or custom orchestration frameworks.
• Routing & Switching: Strong understanding of BGP, EVPN, VXLAN, and Data Centre Interconnects (DCI).
• Hardware Platforms and Cloud‑Native Networking: Proficiency with Kubernetes networking and container‑based infrastructure, including CNIs (e.g., Calico, Cilium).
• Linux Proficiency: Confident with CLI environments, scripting, and diagnostics.
• Automation & Tooling: Experience with Ansible and Python. Familiarity with Terraform or similar infrastructure‑as‑code tools is a plus.
• Customer‑Facing Skills: Comfortable explaining complex networking concepts to customers and internal stakeholders, from engineers to executives.
• Operational Support: Hands‑on experience in L3/L4 support within production environments, driving root cause and preventative measures.
• Engineering Discipline: Strong proponent of code quality, peer reviews, change control, and infrastructure versioning.

Preferred Qualifications

• Industry certifications such as JNCIE, CCIE, or equivalent.
• Familiarity with network security frameworks and best practices.
• Experience with hybrid cloud and cloud connectivity solutions (e.g., AWS/Azure Direct Connect).
• Exposure to observability platforms and time‑series databases (e.g., Grafana, Prometheus, InfluxDB).

Qualities we look for

• Set the standard: Every single day, you spot opportunities to constructively shake things up.
• Inspire the change: There's no blueprint for the future. You’ll embrace challenges and change.
• You’re real and you’re true to yourself: We cherish and celebrate diversity so you’ll feel right at home, whoever you are and whoever you’re talking to, you treat everyone the same.

Benefits

• 30 days of annual leave: we value your peace of mind. With 30 days off (excluding public holidays) and access to mental health resources, we make sure you're as strong mentally as you are professionally.
• A culture that emphasises results over hierarchy, process & ego: we place great emphasis on the quality, ingenuity and creativity of work.
• Open communication, regular feedback: we value smooth collaboration, direct and actionable feedback, and believe that leading with empathy and a growth mindset makes us better together.
• Learning Time: we all have dedicated learning time to focus on new skills, projects or interests that lay outside of your day‑to‑day job.
• Health & Wellbeing: we want everyone to feel healthy and happy, so we offer private medical insurance via Bupa.
• Cycle to Work Scheme: we're committed to building a sustainable business, so we encourage cycling to work.
• Gympass subscription to a variety of gyms and wellbeing apps.
• Participation in the company shares program.
• Enhanced parental pay & leave.

Diversity, Equality, Inclusion and Belonging

We are an equal opportunity employer and we strive to reduce unconscious bias throughout our hiring process. All applicants will be considered for employment without attention to ethnicity, religion, sexual orientation, gender identity, family or parental status, national origin, veteran, neurodiversity status or disability status. To ensure our recruitment processes provide an equal opportunity for all applicants to succeed, we encourage you to let us know if there are any adjustments that we can make.