Senior AI Infrastructure Engineer

We’re looking for Senior+ AI Infrastructure Engineers to build the systems that train and serve Fin's next generation of AI products. Fin is an AI company that builds from the GPU all the way up to a user agent that resolves millions of customer service queries a month. You’ll join a small, highly technical team working at the cutting edge of modern AI infrastructure. The AI Infra team built the training pipelines and runs the inference for custom models like Fin Apex, which outperforms frontier models in customer service tasks, and is the foundation of the AI Group's full stack approach to AI.

• Implement and scale training pipelines for large transformer and LLM models, from data ingestion and preprocessing through distributed training and evaluation.
• Build and optimize inference services that deliver low‑latency, high‑reliability experiences for our customers, including autoscaling, routing, and fallbacks.
• Work on GPU‑level performance: tuning kernels, improving utilization, and identifying bottlenecks across our training and inference stack.
• Collaborate closely with ML scientists to implement cutting edge training and inference methods and bring them to production.
• Play an active role in hiring, mentoring, and developing other engineers on the team.
• Raise the bar for technical standards, reliability, and operational excellence across Fin's AI platform.

• 5+ years of experience in software engineering, with a strong track record of shipping high‑quality products or platforms.
• Degree in Computer Science, Computer Engineering, or a related field (or equivalent experience with very strong fundamentals).
• Hands‑on experience with one or more of: model training (especially transformers and LLMs), model inference at scale (especially transformers and LLMs), or low‑level GPU work (e.g., writing CUDA or Triton kernels).
• Comfortable working in production environments at meaningful scale (traffic, data, or organizational).
• Communicate clearly, explain complex technical topics to different audiences, and enjoy close collaboration with both engineers and non‑engineers.
• Take pride in strong technical fundamentals, love learning, and are willing to invest in your own development.
• Deep knowledge of at least one programming language (e.g., Python, Ruby, Java, Go, etc.).

• Experience at AI native companies that train and/or run inference for their own models.
• Experience running training or inference workloads on Kubernetes.
• Experience with AWS or other major cloud providers.
• Production experience with Python in ML or infrastructure contexts.
• Demonstrated passion for technology through personal projects, open source, meetups, or publishing content.

• Competitive salary and equity in a fast-growing start-up
• We serve lunch every weekday, plus a variety of snack foods and a fully stocked kitchen
• Regular compensation reviews - we reward great work!
• Unlimited access to Claude Code and best-in-class AI tools; experimentation & building is encouraged & celebrated.
• Pension scheme & match up to 4%
• Peace of mind with life assurance, as well as comprehensive health and dental insurance for you and your dependents
• Flexible paid time off policy
• Paid maternity leave, as well as 6 weeks paternity leave for fathers, to let you spend valuable time with your loved ones
• If you’re cycling, we’ve got you covered on the Cycle-to-Work Scheme. With secure bike storage too
• MacBooks are our standard, but we also offer Windows for certain roles when needed.

Fin has a hybrid working policy. We believe that working in person helps us stay connected, collaborate easier and create a great culture while still providing flexibility to work from home. We expect employees to be in the office at least three days per week.