Most backyard basketball courts for homes are 60 feet by 90 feet in size and dimensions.
The 60 feet by 90 feet is a perfect size for a backyard basketball court but you could go a bit larger or smaller if you desire.
But to allow enough room to play basketball I would not go much smaller than 60 feet by 90 feet unless you don't have the room for that size.
Having a small basketball court out of concrete would be better than no concrete basketball court though but the larger you make the basketball court the better off you'll be.
50 feet by 94 feet is the regulation size for basketball courts for the NBA but you can make your home basketball court larger or smaller depending on the size of your backyard and how much room you have for the basketball court.