Hey thanks for the response and suggestion. The IDs were actually meant to all be unique by changing one letter for each one, I should’ve used simpler IDs. And now strangely it seems I can’t edit the post. Anyways I want to identify groups based on if the groupedMsgs follow each other when they’re sorted by time (i.e. the date property). So the second and third messages would be a group containing 2 items because they come after each other, but the fifth would be another group of 1. I haven’t found a pipeline using $group that achieves this, once I add the type as a group ID then all the groupedMsgs get put into that group.