.Q namespace functions can (and should!) be used –> they are very useful in lots of different situations. However it is safest to only use .Q functions that are documented on the .Q reference card found here: https://code.kx.com/q/ref/dotq/.
Using any other undocumented .Q namespace functions (or any other undocumented namespace function) may cause issues as these are what we call ‘exposed infrastructure’