I've been working with a Magento 1.9 shop that has issues with their speed, and I've noticed turning off the 'Is Anchor' in Category settings speeds up the category view significantly.
I understand this removes the layered navigation on the left, which is why the speed increase happens. I'm just wondering if it does anything else in the background I should know about, or any other 'side effects' that I should know about before turning it off on all categories?
As I noticed when I turn off 'Is Anchor' in a certain category the number of products displayed next to the category name goes from 400 down to 11 which worried me a bit.
Some of their category pages even have custom views where the layered navigation doesn't even show but 'Is Anchor' is still set to 'Yes' so I imagine it's pointless being on especially on those categories?