Carts/update event -> Is cartId always unique?

[learnerSquad]

I am consuming cart/update events which contains cartId. lets say initially cartid is cart1 & user completes the purchase then next time the cartid would be different i.e. cart2. So If I assume that at no point in future cart1 id be assigned to any cart, would I be correct in my assumption?

Asking this question because I am going to keep a map of cartId to fingerprint id in my Database & for my use case to work properly, the cartId should always be unique.