Callosum

About Us Artificial intelligence scaled on a bet - that bigger models, more identical chips, and more data would keep delivering. As problems grow more complex and the requirements of intelligence more diverse, that bet is breaking down. The next era belongs to heterogeneous intelligence: diverse models on diverse chips, each with distinct strengths, co-evolving into systems of capability unreachable by any single model or accelerator. Callosum is the Intelligent Systems company. We built the infrastructure to make that possible. Our co-evolution engine optimises simultaneously across workflows, agents, and silicon. We launched in early 2026 showing orders of magnitude improvements in performance and a shift in the cost-performance frontier that no single chip or model provider can provide. We believe intelligence comes from the system, not the model. We are scientists and engineers solving what others consider impossible. If you thrive on hard problems, and are passionate and energised by the scale of the challenge, we would love to hear from you. About the Role As a Staff Platform Engineer, you will design and build the infrastructure that makes our heterogeneous intelligence API scalable and efficient in production at high throughput and rapidly growing scale. This spans the full platform stack: API design and reliability, Kubernetes-based deployment, observability, and cloud infrastructure. The role sits at the intersection of platform engineering, backend infrastructure, and DevOps. As the ideal candidate, you combine deep expertise in backend system design and cloud-native infrastructure, and is comfortable owning hard problems in a fast-paced and highly collaborative environment. You will be working closely with the hardware and orchestration teams. The role has strong growth potential toward technical leadership in platform architecture as we expand our heterogeneous compute infrastructure. Responsibilities Design and build a scalable, robust API platform capable of handling rapidly growing and diverse workloads across heterogeneous compute infrastructure Own Kubernetes-based deployment, and reliability for API services in production Own platform observability - metrics, tracing, and alerting across the full platform Manage cloud infrastructure (AWS) and deployment pipelines Work closely with the hardware team to maintain and expose hardware deployment capabilities through the API layer Qualifications Strong experience designing and operating high-throughput APIs (REST or gRPC) with high performance requirements Strong hands-on experience with Kubernetes in production - deployment, autoscaling, failure recovery, networking; comfortable owning a cluster, not just deploying to one Solid cloud infrastructure fluency (AWS preferred) and hands-on experience with infrastructure as code Solid understanding of observability tooling Nice to Have Experience with developer tooling Experience as a user or builder of AI-native developer products What We Offer Competitive Salary: £101,000 - £192,000, determined by skills and experience Equity & Ownership Private healthcare We offer Visa sponsorship and relocation benefits to hire the best in the world We work in person at our London office. You'll have the tools, space and setup to do your best work, and if you have specific needs, just tell us We're committed to building an inclusive workplace where everyone feels welcome, and believe in equal opportunities for all.