Do pros ride with 1X configuration on some courses? I'm looking at the first stage of the Tour of California, which is on a flat course (around Long Beach, USA).

Since there's no real dénivelé (french, "difference in height"), there is no need for a lot of gears.

So, do pro riders sometimes use 1X configuration on their bikes, either on criterium races or on flat courses, or on flat time trial courses?
Yes, they sometimes do (or at least announce/intend to), here are two examples:


  This is the 3T Strada that Aqua Blue Sport will ride in 2018, making
  the Irish-based squad the first pro cycling team to use a
  single-chainring drivetrain.


Source


  One ring to rule them all: Tony Martin's Canyon Speedmax 58x11-32 on
  the world champ's time trial rig


Source