Android Room persistence library @Update not working

Make sure the row you want to updated and model you are sending to update should have same id which you have defined as primary key.

I am sorry for posting this as an answer but I am not allowed to add a simple comment yet so here is my idea:

Have you tried using only insertCars() instead of updateCars()? Anyway it looks like your isCarsEmpty() LiveData callback gets triggered the whole time because when the observer is called the Database is altered again.. I am not quite sure what you want to accomplish tho.