O(log n) is ok with small data, let's say up to thousands. But when you've millions or billions of record also the O(log n) takes time. It's about size. Until y

O(log n) is ok with small data, let's say up to thousands. But when you've millions or billions of record also the O(log n) takes time. It's about size. Until yesterday we managed small database in comparison to the today's BigData-Base. That's why a Graph Database makes sense today, much more than yesterday.