One trick I didn't mention in the article: partially nullable unique indexes. The idea is you want multiple rows to be able to half-claim a value, but only one

One trick I didn't mention in the article: partially nullable unique indexes. The idea is you want multiple rows to be able to half-claim a value, but only one to really claim it. The value goes in the non-nullable column, and the second column is a nullable "claimed" column that is set to 1 to claim it. I haven't been able to think of any real use-cases for this though.