That five minute question may well save you an hour of work, but it's just as likely - I'd say_more_ likely - to steal an hour of productivity from the person y

That five minute question may well save you an hour of work, but it's just as likely - I'd say_more_ likely - to steal an hour of productivity from the person you ask. Just send them a message in slack. Don't be so obnoxious as to assume that whatever's bugging you at this moment is automatically more important than whatever your co-worker is on. I don't know why it feels weirder to slack them then it does to turn your head and ask. One demands immediate attention, the other allows them to answer when they have bandwidth for it. It seems obvious enough to me which is more polite.