Bulk head is a pattern designed to ensure that no part of the system deeply impacts other system areas. The name comes from a common solution used in ships to ensure that if there is a hole in the hull, it doesn't lead to the boat sinking.
Here, for instance, the second area has a hole and the water is coming into the section but the boat will not sink, as the other sections are isolated.
The Titanic used this technique but the isolation was not fully done from down to top for passengers and crew members comfort. And we all know the outcome of that choice. That is why, if you go with isolation, it is important to make sure that it is complete; otherwise better not do anything.
What does it mean for an application? It means that each service that can sink your application should be isolated from the other ones. This isolation is mainly about the execution and, therefore...