I said this already, and I will say it again: SQL Server optimizer is smart. I can even go further and say, it’s smarter than you and me (I have no doubt that you are smart, even very, very smart 🙂 ). So most of the cases, you leave it to do whatever it thinks is the best.
But there are cases SQL Server optimizer is fooled by the engine – it gets confused and chooses an sub-optimal plan, because it was given wrong, outdated, or incorrect information. That’s when you need to step in.
Today I face one case like that, as reported here: http://world.episerver.com/forum/developer-forum/Episerver-Commerce/Thread-Container/2017/10/database-timeout-on-productvariant-update/