LAS VEGAS — Benoit Dupin, Apple’s senior director of machine learning and AI, has been at AWS re:Invent before, as the VP of search technology for Amazon’s A9 division, but this was a new twist.

Dupin was the first surprise guest on stage Tuesday morning at the re:Invent conference in Las Vegas, where Amazon Web Services CEO Matt Garman is delivering his first keynote in the role.

It was a high-profile endorsement for Amazon in its AI race against cloud rivals Microsoft and Google.

Dupin talked about Apple’s extensive use of Amazon services for products and services including iPad, Apple Music, Apple TV, News, App Store, and Siri, as well as AWS’s behind-the-scenes role in Apple Intelligence.

He said Apple has used AWS chips like Amazon Graviton and Inferentia to achieve more than 40% efficiency gains in its machine learning inference workloads compared to x86 instances.

Apple is also in the “early stages of evaluating Trainium 2,” the latest version of the AWS AI training chip, the general availability of which was announced by Garman earlier in his talk. Based on its early experience, Dupin said Apple expects to see up to a 50% improvement in efficiency when pre-training its models on the Trainium 2 instances.

Announcements in Garman’s keynote so far have been focused on the company’s EC2 core cloud computing business, and the company’s Tranium and Inferentia chips for AI workloads.

We’re also awaiting an appearance by Amazon CEO Andy Jassy in his first return to the event since becoming Amazon CEO a few years ago.