Dog sleeps facing the door always?

I’ve noticed my dog always sleeps/rests facing our front door. We live in a tiny apartment so our bedroom is very close to the front door.
At night time when she’s in bed with us, she always positions her body so that her head is facing the front door. During the day, she chills on her dog bed in the living room - where she usually faces the door as well.

I’m wondering if this is something common that dogs do? I’m not sure if this means she’s always on guard or stressed. She’s a lab mix.