Flying FR for the first time, from CGN to STN, on a late evening flight.

No luggage, boarding pass already on my phone, fast track at security, paid highest fare - so basically I cut out all factors that could slow me down. Remaining question: when do they close the boarding gate? Not the "we recommend to be at the airport x hours before departure" time (where you end up wasting time watching the paint dry on the walls) but the time after which they no longer scan boarding passes and don't let people through the gate anymore? I'll build in some buffer, but I'd need to know whether I have to add my buffer to "departure-10 minutes" or to "departure-30 minutes".

Thanks!