How to join two payloads, when one is intermittent?

[knolleary]

@nodecentral

How does the join decide which of the incoming topics to use as the key ?

That question doesn't really make sense. It doesnt decide because it handles each message as it arrives. The message has a tooic, the join node will add that message to it's output object, using that message's topic as the key and it's payload as the value.