Principal Machine Learning Engineer

As a Principal Machine Learning Engineer, the work centres on leading the end‑to‑end development and productionisation of LLM‑based systems, from upstream training and reinforcement learning (RLHF/RLAIF) through fine‑tuning, alignment, and de. It would suit someone who can bring strong professional approach to the role.

What the work leans on

Our Principal Machine Learning Engineers are technical leaders who shape the direction of intelligent systems across Apple. You will design and build production‑grade inference systems, working across Swift, Java, and Python to integrate ML capabilities seamlessly into Apple's ecosystem.

Where the technical work sits

• Leading the end‑to‑end development and productionisation of LLM‑based systems, from upstream training and reinforcement learning (RLHF/RLAIF) through fine‑tuning, alignment, and deplo.
• Mentor and elevate ML engineers across the team, raising the bar on technical quality and fostering a culture of rigorous experimentation and engineering craft.
• Driving model customisation and adaptation strategies (prompt engineering, retrieval‑augmented generation, parameter‑efficient and full fine‑tuning) to deliver differentiated product.

Technical requirements

• Experience with multimodal AI systems (text, image, code, speech) and cross‑modal reasoning.
• Extensive hands‑on Machine Learning engineering experience, with a demonstrable track record of shipping ML‑powered products at scale.
• Experience with pre‑training or continued pre‑training of large language models, including data curation, curriculum design, and training stability at scale.

What helps delivery stay steady

Strong professional approach.

Practical details

• At Apple, we build AI systems that define experiences for billions of people and we do it with an unwavering commitment to privacy, performance, and craft.
• If you thrive at the intersection of frontier model development, systems engineering, and product creation we want to hear from you.
• London, England, United Kingdom Corporate Functions.
• The ideal candidate is equal parts researcher, engineer, and product builder.

Job details

• Benefits mentioned: Training