Apple CEO Tim Cook has no public plans to retire, but last year when succession plans were discussed, one of the names that popped up was John Ternus.

Currently the Senior Vice President for hardware engineering at Apple, Ternus joined the famed product design team in 2001. Born in 1975, Ternus earned his degree in mechanical engineering from the University of Pennsylvania, and also represented the school as a competitive swimmer. After graduating, he spent four years at Virtual Research Systems before joining Apple.

Ternus initially worked on external Mac monitors, but as his career took off, eventually focused on Apple's mobile products, overseeing every model of the iPod as well as the latest editions of the iPhone, and the development of AirPods — and has led the transition of the Mac to Apple's own silicon, the company notes.

"I started in product design… I'm a mechanical engineer by background," he said in an interview with CNBC last year. "I've had the great fortune of working on pretty much every type of product that we make."

Of the Mac transition to in-house silicon, Ternus said it was a fun project in part because of the dedicated user base. "We were able to work together to develop an architecture that was perfectly suited for the kinds of things our Mac users do."