The position, which Bezos created more than a decade ago, serves as his sounding board on key decisions, sits with him during daily meetings and confers with him to close most workdays. It has been described as the most coveted job at Amazon, according to Bloomberg Businessweek. Shadows usually last approximately two years in their role, according to Business Insider. Bezos got the idea to implement the technical advisor position from venture capitalist John Doerr.

Previous shadows include Andy Jassy, now head of the company’s Amazon Web Services unit; Amit Agarwal, VP and Country Manager of Amazon India; Greg Hart, VP of Amazon Echo; Dilip Kumar, a VP at Amazon presentlyworking on a closely guarded project; and Ian Freed, VP of Amazon Devices who oversaw marketing of the Fire Phone before taking a sabbatical.

The appointment of Renz to the position could influence the future executive structure of the company. Presently, Amazon has seven executive officers in addition to Jeff Bezos, but only one, Worldwide Controller Shelley Reynolds, is a woman.