Spikes doors were introduced in "The Market" update. Door spikes have the features of both doors and spikes, which means that they do damage on contact and can be opened at the same time. Their main disadvantage is that they deal half the damage that normal spikes would deal and have very little health compared to other structures. It also is harder and takes more time to craft.
The first Door Spike upgrade, it deals 5 damage to players on contact. Wooden Door Spikes are very weak, having less durability than a Campfire. It also deals a meager 5 damage. Because of this, it is not recommended to use these on a base.
Second upgrade, does not upgrade from the Wooden Door Spike but from a Stone Door. It has better damage (10), but still very low durability. It does less damage than a Wooden Sword.
Third upgrade, far better than stone spike. The durability is still very low though.
Fourth upgrade, greater health and damage (20). It could fit very well in a base, and can be found in advanced bases.
Amethyst Door Spikes are the fifth upgrade of door spikes. They have a lot more health (2 times the diamond tier) and they deal 25 damage upon contact, a bit more than the damage a Diamond Sword does. They can be found in very advanced bases.