Key Skills

Job Description

What we do Circle B builds sustainable IT infrastructure for the AI and cloud era. For over a decade— we have designed and deployed datacenter, edge, and AI/HPC systems on Open Compute Project (OCP) hardware. We are independent, vendor-neutral, and ISO 9001 / 14001 / 27001 certified, with deployments across multiple countries. Our newest initiative is a sovereign EU GPU cloud — operating under full Dutch/EU jurisdiction and beyond the reach of the US CLOUD Act, for regulated European organizations that cannot compromise on where their data lives. The Role You own the network end to end: the fabric that carries GPU traffic, the segmentation that keeps tenants and zones properly isolated, and the routing, firewalling, and load balancing that connect customers to compute. What you will own The lossless GPU fabric across 800G-class switches, tuned for predictable RDMA performance. On Ethernet that means PFC, ECN, and DCQCN; on InfiniBand, the subnet manager and congestion control. Collective-communication (NCCL) performance across the fabric, working with the Infrastructure Engineer who owns the host side. Multi-zone segmentation: the revenue zone, the air-gapped sovereign zone, the management and internet zone, and the out-of-band network. The L2/L3 design: BGP, EVPN/VXLAN or the equivalent, VLANs, routing, and the controlled paths between zones. Firewalling and zero-trust at L3/L4: micro-segmentation, ACLs, and ingress/egress policy. Load balancing and ingress for platform and tenant traffic. The out-of-band and BMC management network. Datacenter interconnect and any carrier or cross-connect work at AMS3. Fabric automation: switch configuration, validation, and drift detection as code. The telemetry the Platform Engineer needs: error counters, congestion metrics, and link health. What We Are Looking For Required 7+ years in network engineering, including 4+ years building and running production datacenter fabrics. Deep production experience with a high-performance lossless fabric: either RoCEv2 Ethernet (PFC, ECN, DCQCN) or InfiniBand (UFM, subnet manager, SHARP). Real experience, not just lab familiarity. Strong BGP and EVPN/VXLAN in a Clos / spine-leaf design: ECMP, fast convergence, QoS, and jumbo frames. Production experience on a modern switch OS such as SONiC, NVIDIA Cumulus Linux, or Arista EOS. Network automation with Python, Ansible, and gNMI or vendor APIs: configuration and validation as code. Segmentation and firewalling for multi-tenant or regulated environments. Self-directed: you diagnose, propose, carry it out, and document. Nice to have Hands-on with NVIDIA Spectrum-X (Ethernet) or Quantum InfiniBand on the current 800G switch and ConnectX-8 / BlueField generation. 400/800G optics and high-radix switches at scale: link bring-up and fault isolation under load. Rail-optimised or fat-tree topologies and GPU collective traffic (NCCL, GPUDirect RDMA). Familiarity with the NVIDIA Cloud Partner (NCP) reference architecture and its network model. Streaming telemetry (Prometheus, Grafana, gNMI). Regulated, sovereign, or air-gapped network design, and awareness of GDPR, DORA, NIS2, and NEN 7510. Experience at a GPU cloud, AI provider, HPC centre, or a low-latency trading environment. Why Join Us Help build a sovereign EU GPU cloud from the ground up. Own a critical platform layer, not just tickets or maintenance. Work on modern AI infrastructure, GPU platforms, Kubernetes, observability, and automation. Join a company with deep experience in OCP, datacenter, AI/HPC, and cloud infrastructure. Build infrastructure for organizations where data location, compliance, and reliability truly matter. Benefits Competitive salary. Pension scheme. Visa sponsorship. Company gym. Modern office in Hoofddorp. Informal and open working culture. Participation in relevant conferences and exhibitions across Europe. Opportunity to develop your skills in a fast-growing technology environment. Our Work Culture Circle B offers an informal working atmosphere with energetic people who enjoy being part of a growing technology company. We have an open management culture and encourage colleagues to contribute to improving our products, services, and processes. If this sounds like a good fit, please send your CV and motivation letter to: [email protected]

Core Responsibilities

Own the end-to-end GPU network fabric, including lossless Ethernet or InfiniBand performance, multi-zone segmentation, routing, firewalling, load balancing, and datacenter interconnects. Automate switch configuration and validation, monitor fabric health and congestion, and collaborate with infrastructure colleagues to optimize GPU collective communications.

Requirements

Requires at least seven years of network engineering experience, including four years building and operating production datacenter fabrics, with hands-on experience in RoCEv2 or InfiniBand. Candidates should also have strong BGP and EVPN/VXLAN skills, experience with modern switch operating systems, network automation, and segmentation or firewalling in multi-tenant or regulated environments.

Benefits

• Pension Scheme
• Visa Sponsorship
• Company Gym
• Modern Office
• Conference and Exhibition Participation
• Professional Development Opportunities