Fast Lookup in Flow can use 15 or 18 character ID

Just in case you were wondering, fast lookup element in flow can use a 15 or 18 character ID.

I have a flow that uses custom metadata type to determine which parent record to use, and I created two MDT records - one w a 15 character ID and one w an 18 character ID. Both worked

However, if you are trying to do a comparison to say check if an ID is already in a collection, then 15 and 18 are not equivalent, and you must stick with one length. I say stick w 18, b/c flow will save record as 18

I see in a SFSE thread that global variables such as User.Id will resolve as 15 character IDs, but Account Owner comes through as 18 character ID…so there is some murkiness under the covers. Best to stick w 18 and throw caseSafeId on the IDs, though you could also just use a LEFT function on all IDs…