Agreed, and displaying this like a tree is then a UI concern. I think you'd get slightly more performance if you were to store "Folder" and "Key" separately --

Agreed, and displaying this like a tree is then a UI concern. I think you'd get slightly more performance if you were to store "Folder" and "Key" separately -- either three fields or using a parent-child table. You'd be able to index "Folder", and it would make building the tree structure itself easier and more efficient, and looking up all the values in a specific tree simpler.