HPC Network Engineer

Fuse Energy is an energy startup on a mission to make energy abundant and affordable, fast. We combine first-principles thinking with cutting-edge technology to build a radically better energy system. We've raised over $200M from top-tier investors including Balderton, Lakestar, Accel, Creandum, Lowercarbon, Ribbit, 20VC, Hummingbird and Collaborative Fund, alongside strategic angels including Nico Rosberg and GPs behind Meta, Revolut, Spotify and Uber. We're building a fully integrated energy company: developing our own solar, batteries and other generation projects, building our own hardware, improving and developing grid infrastructure, trading power in real time, using AI across the business, and installing distributed energy in homes. By selling directly to consumers we cut out the middleman, lower costs and pass the savings on to our customers. You'll design, deploy and operate the network fabric for our multi-tenant AI cluster: the high-performance compute and storage fabrics carrying RDMA traffic between GPUs, the tenant-facing and management networks, firewalling and tenant isolation, and the out-of-band infrastructure that keeps it all recoverable. Beyond the data centre, you'll own the office network and act as the networking authority for the company. You own the fabric from architecture through day-2 operations. Responsibilities Design and operate lossless, RDMA-capable fabrics (e.g. RoCEv2, InfiniBand) for GPU compute and storage traffic, including QoS, congestion control and buffer tuning at scale Build and manage leaf-spine data centre fabrics, with routed underlay and overlay design (e.g. BGP, EVPN/VXLAN) Implement and maintain per-tenant network isolation across compute, storage and management planes Automate network provisioning, configuration and validation, treating switch config as code (e.g. Ansible, Python, NetBox as source of truth), deployed through CI Build telemetry and observability for the fabric: flow-level and buffer-level visibility, dashboards and alerting that catch congestion and link degradation before tenants do Troubleshoot performance issues end to end, from optics and cabling through switch buffers to NIC/DPU configuration and collective-communication behaviour on the hosts Operate the out-of-band management network, console access and remote recovery paths Support tenant onboarding: segmentation and addressing, bandwidth and isolation guarantees, and capacity planning as the cluster scales Write clear design documentation capturing decisions, rationale and rejected alternatives Own and maintain the office network: wired and wireless infrastructure, firewalling, VPN/remote access and office-to-data-centre connectivity Upskill colleagues on networking through documentation, run-throughs and pairing Requirements 5+ years as a network engineer operating production data centre networks Strong dynamic routing experience (BGP in particular), plus overlay/encapsulation design and…