Handling the same event on multiple projection partitions

Have been looking at whether it’s possible to handle the same event on multiple partitions (or broadcast a change to other partitions) and then trigger a result output. Simple use case is a list on one partition and items on their own. One item can be in multiple lists. Each list and its added items are in a single stream. When an important property of the list is changed an event is raised and handled by the list partition. Looking for thoughts on how to handle it on the related item partitions too?

Ideas I have had so far:

  • Use shared state, but that doesn’t seem to trigger results on other partitions.
  • “Internally” emit an enriched event back to the same projection. This seems to work, but seems to be fragile.
  • Pre projections that emit the necessary additional enriched events. Works but splits logic.

P.S. Kudos to the team on the 4.0.3 release, UI tweaks and bug fixes are excellent.