AI System Architect

THE OPPORTUNITY Lumai is redefining how the world computes. We are an ambitious, venture-backed UK startup pioneering a breakthrough AI accelerator for data centers which uses 3D optical compute. Our radical technology uses light to perform computation at orders of magnitude faster speeds and at far greater scales than ever before, all whilst consuming far less energy than traditional approaches. Lumai is unlocking performance and efficiency gains that could transform the economics of AI and compute infrastructure and reshape how intelligence scales globally. If you are passionate about bringing groundbreaking technology to market, and want to be part of a team pushing the boundaries of what is physically possible, Lumai is where you can make it happen. ABOUT LUMAI Founded in 2022, Lumai is a University of Oxford spinout using optical processing to accelerate large language models (LLMs) and other transformer-based AI systems. The team combines expertise in optical computing, machine learning, and physics. Lumai has already secured over $15 million in investment from leading deep-tech investors like Constructor Capital, IP Group, PhotonVentures and government grants, and is scaling rapidly to deploy the fastest optical compute currently available globally. THE ROLE We are looking for a System Architect who thinks in AI first and hardware second. You will own the architectural vision that bridges our AI workload requirements with our silicon and software execution. This is not a role for someone who designs chips and then asks what AI runs on them — it's a role for someone who deeply understands AI models, inference and training pipelines, and then works backwards to define the hardware and software systems that serve them best. You will sit at the intersection of leadership, hardware engineering, and software engineering — translating high-level product strategy into concrete architectural decisions and ensuring all three teams are aligned, unblocked, and pulling in the same direction. WHAT YOU'LL DO Architecture & Technical Leadership - Define and own the end-to-end system architecture, from AI workload characterisation through to chip microarchitecture trade-offs and software stack interfaces - Drive architectural decisions by starting with AI model and operator analysis — identifying compute, memory bandwidth, data movement, and sparsity patterns that constrain and shape the hardware design - Develop and maintain architectural specifications, performance models, and design documents that serve as the single source of truth across teams - Evaluate architectural trade-offs (latency vs. throughput, on-chip vs. off-chip memory, dataflow strategies, precision formats) with a quantitative, workload-grounded methodology - Stay current with the frontier of AI research (model architectures, training techniques, inference optimisations) and translate emerging trends into architectural foresight Cross-functional Coordination - Act as the primary technical bridge between the leadership team, hardware engineering, and software engineering — ensuring that decisions made in one domain are properly communicated, challenged, and integrated in others - Partner with the leadership team to translate business goals and product roadmap into architectural requirements and phased execution plans - Work closely with the hardware team to ensure microarchitectural decisions are grounded in realistic AI workload demands; push back constructively when hardware-centric thinking diverges from AI requirements - Collaborate with the software team to define clean hardware/software interfaces, programming models, and runtime abstractions that make the hardware genuinely usable for AI practitioners - Facilitate architectural reviews and design discussions that create shared understanding rather than siloed decision-making Execution & Delivery - Identify and resolve cross-team dependencies and ambiguities early, before they become schedule risks - Define and track key architectural metrics and milestones throughout the chip development lifecycle (pre-RTL through tape-out and post-silicon validation) - Support benchmarking and performance analysis efforts, helping teams understand where the system delivers against AI workload targets and where it falls short WHAT WE'RE LOOKING FOR Must-Have - Deep, hands-on understanding of modern AI/ML workloads — transformer architectures, convolutional networks, recommendation systems, or similar — including their compute and memory access patterns - Proven experience defining system or chip architecture in the context of AI/ML acceleration (inference, training, or both) - Ability to build and use analytical performance models (roofline models, memory bandwidth analysis, cycle-accurate estimates) to guide architectural decisions - Strong communication skills with the ability to adapt technical depth for leadership, hardware engineers, and software engineers alike - Experience working across hardware and software boundaries — comfortable discussing ISA design, compiler interfaces, and runtime scheduling as well as datapath microarchitecture - Suitable University education and/or practical experience Strong Preference For - Experience at an AI chip startup, AI hardware team at a major tech company (e.g. Google TPU, Meta MTIA, AWS Trainium/Inferentia, Tesla Dojo), or a leading fabless semiconductor company - Familiarity with AI compiler stacks (MLIR, XLA, TVM, Triton) and how they interact with hardware architecture decisions - Understanding of chip development processes: RTL design, physical design constraints, and post-silicon bring-up - Experience with or exposure to on-device / edge inference as well as datacenter-scale deployments - Track record of influencing architectural direction through written specs and data-driven arguments rather than authority alone WHAT SUCCESS LOOKS LIKE In your first 90 days, you will have audited the current architectural approach against a defined set of target AI workloads, identified the top architectural risks to schedule and performance, and established a working rhythm with the HW and SW leads. Within six months, you will be the person who others come to when a cross-team decision needs an owner — and the one who keeps the architecture honest against the AI workloads we are building for. COMPENSATION & BENEFITS - Highly Competitive Salary: We are not saying our salary is a blank check, but let's just say it won't be a source of your stress - Share Option Scheme: We are all in this together! We believe in shared success while we build the Lumai of tomorrow - Pension Scheme: Plan for retirement with AVIVA - Private Health Insurance: We firmly believe that you come first, and a happy you is a healthy you! Look after yourself and your loved ones with AXA - Cycle to Work: Spread the cost of a bike, a bike and accessories or just accessories and save on tax - L&D Allowance: Stay at the forefront of your field with a £500 annual development budget - Subsidised On-site Lunches: Enjoy on-site healthy meals at half the price, as Lumai covers 50% of the cost - Holidays: Enjoy some deserved "me time" with 25 days paid holiday (plus bank holidays) per year - Socials: Be part of an inclusive community enjoying occasional all-company off-sites, lunches and socials INTERVIEW PROCESS Our process is four stages. An initial conversation with our HR team to understand what you want from the role and what we want from it. Two technical sessions with various members of our engineering team. Finally, an HR-team session covering scope, terms, and any final questions. We aim to move fast on candidates we are excited about; expect roughly three to four weeks end to end. Lumai is an equal opportunity employer. We make hiring decisions on merit, scope-fit, and the strength of the working relationship we expect to build with each hire. Applications welcome from candidates of any background. If you are not sure whether you are a fit, send a note anyway.