Experience from FOSDEM that happened last weekend: all talks had been pre-recorded and started exactly on time. During the talk, an active room of chat discussi

Experience from FOSDEM that happened last weekend: all talks had been pre-recorded and started exactly on time. During the talk, an active room of chat discussion. At the the end of the talks, speakers join the room to address (some of) the questions that have been raised and not already answered. Then, a separate video-conference room becomes available, for anyone who wants to continue discussing with the presenters, while the next talk starts. The combination of prepared (async) presentations and live (synchronous) QnA sessions was a sweet spot. And the scale... 774 talks in 108 different "rooms" (and a video-conference after each one of them). All implemented with Free Software.