However for those not well known by check-in staff and not so familiar with the airport, I would suggest not cutting it that fine. It can take 30 minutes getting through security alone at busy times.

My rule of thumb for international is be at the check in no later than 1 hour before departure, although I generally aim to be earlier than that (allows for getting caught in traffic on the way to the airport, accidents, change of airport layout forcing long walk, etc).