Small sample size but Garrett appears woefully inexperienced yet exceptionally fast tracked:
Mike Patricia
1996-1999: Patricia remained at RPI to begin his coaching career as a graduate assistant in 1996. He spent the next two years as an application engineer with Hoffman Air & Filtration Systems in East Syracuse, New York. Much sought-after in engineering circles, he received a $100,000-a-year offer to maintain nuclear submarines and aircraft carriers with the Westinghouse Electric Company
1999-2000: return to football as the defensive line coach for Amherst College
2001-2004: Syracuse University as an offensive graduate assistant for the team
2004-2005: Patriots offensive coaching assistant
2005-2006: Patriots' assistant offensive line coach.
2006-2011: Patriots linebackers coach
2011-2012: Patriots safeties coach
2012-2018, Patriots defensive coordinator, though he had been calling the plays on defense since the departure of Pees following the 2009 season.
(The Patriots won three Super Bowls with Patricia: Super Bowl XXXIX, and Super Bowl LI)
Sean McVay
2008-2010: assistant wide receivers coach with the Tampa Bay Buccaneers
2009-2010: wide receivers/quality control coach for the Florida Tuskers of the United Football League (UFL)
2010-2011: assistant tight ends coach for the Washington Redskins
2011-2013: Redskins tight ends coach
2014-2016: Redskins Offensive coordinator
2017: LA Rams head coach
Jason Garrett
2005–2006: quarterbacks coach for the Miami Dolphins
2007-2010: Dallas Cowboys as offensive coordinator
2011-2018: Dallas Cowboys head coach