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.

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, Photon Ventures and government grants, and is scaling rapidly to deploy the fastest optical compute currently available globally.

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.

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…