Principal Machine Learning Engineer (Up to £135k + Equity) at Speechmatics

This is a job that Jill, our AI Recruiter, is recruiting for on behalf of one of our customers. She will pick the best candidates from Jack's network. The next step is to speak to Jack. Job Title Principal Machine Learning Engineer Salary Up to £135,000 + Equity Company Description Speechmatics is a $62M Series B speech-to-text intelligence leader based in Cambridge and London, pioneering world-class Voice AI that supports over 55 languages. Job Description As a Principal Machine Learning Engineer, you will co-define Speechmatics’ technical vision while remaining hands-on in the Modelling Team. You will bridge the gap between cutting-edge research and production systems, developing next-generation transformer models and optimizing inference for global scale. This is a high-ownership role focused on shipping real-world impact. Location London, UK Why this role is remarkable * Lead the technical direction of a $62M Series B scale-up that recently saw 4x growth in real-time usage and serves global customers. * Work at the rare intersection of high-rigor ML research and large-scale production, shipping models that solve real-world problems like accents and noise. * Take full ownership of technical domains, raising the bar for a talented team of 10+ engineers while developing groundbreaking bilingual and medical models. What You Will Do * Develop and deploy advanced ML models using Python and PyTorch, translating research into scalable, maintainable production services and services. * Optimise large-scale model inference using strategies like dynamic batching, flash attention, and speculative decoding to improve speed and cost efficiency. * Define and enforce best practices for model lifecycle management, data quality, and evaluations across the entire ML stack. The ideal candidate * Deep expertise in building and shipping production-grade ML systems, with a strong foundation in modern transformer architectures and self-supervised learning. * Proven track record in distributed training and optimizing inference at scale, bridging the gap between research models and production-ready code. * Expert proficiency in Python and ML frameworks such as PyTorch, complemented by experience in MLOps, CI/CD pipelines, and containerization. Who are Jack \& Jill? Ok, I'll go first. I'm Jack, an AI that gets to know you on a quick call, learning what you're great at and what you want from your career. Then I help you land your dream job by finding unmissable opportunities as they come up, supporting you with applications, interview prep, and moral support. And I'm Jill, an AI Recruiter who talks to companies to understand who they're looking to hire. Then I recruit from Jack's network, making an introduction when I spot an excellent candidate. How does this work? * Jack's an AI agent for job searching and career coaching. He works for you. * Jill is the AI recruiter working for the company. She recruits from Jack's network. * If it's a match and the company wants to meet you, they'll make the intro. In the meantime, if you'd like, Jack will send you excellent alternatives. We never post fake jobs This isn't a trick. This is an open role that Jill is currently recruiting for from Jack's network. Sometimes Jill's clients ask her to anonymize their jobs when she advertises them, which means she can't share all the details in the job description. We appreciate this can make them look a bit suspect, but there isn't much we can do about it. Give Jack a spin! You could land this role. If not, most people find him incredibly helpful with their job search, and we're giving his services away for free.