I was thinking, what if I want to add to a relatively small behavior tree 20 or 30 key selectors ( mostly for checks and services), will this amount or more will start taxing overall AI preformance ? Or are they passive and have no influence for preformance ?
Hey @Rexow12!
It would be hardly noticeable, even with a large amount of copies of this actor. A blackboard key is basically just a string variable, so the size is measured in bits and bytes. The checks and services themselves might be more of a performance issue, but the key selectors would be difficult to notice unless you got INCREDIBLY granular. 
Go for it! You’ll be fine! Start thinking about this again if you ever get into the hundreds!