The dependency stack (DependencyStack) is provided by the DepCalc module. This stack is involved in the content import and export processes. It functions as an object map of proxy objects to entities after they are properly loaded.
The dependency stack is usually not visible to developers. However, during various events such as the tamper layer, entities are explicitly manipulated for tracking by the dependency stack.
The dependency stack must always track entities by their remote UUID from the Content Hub service.
Contents of the dependency stack
The dependency stack contains the \Drupal\depcalc\DependentEntityWrapperInterface objects in an object map keyed by remote UUID. The DependentEntityWrapper objects are not entities, but they understand how to retrieve an entity. This approach allows a large number of objects to be placed into a DependencyStack while keeping memory consumption needs relatively low.