This one's permanently stored in my Pinboard — a conversation I had this morning triggered a re-read.

"A user is only part of one team". Until we decide to add multi-team support, and the $user->team BelongsTo relation suddenly needs to be replaced in 50 places.

Golden advice from swyx:

It is a LOT easier to scale code from a cardinality of 2 to 3 than it is to refactor from a cardinality of 1 to 2.