At about 19:35 UTC on January 10, 2017, a very large number of chat flags were sent from the Russian StackOverflow chatroom to every 10k user on the network.
Shortly afterwards, chat began to lag very severely (timeout errors, mostly), finally crashing altogether to the familiar ASPXError page around 19:40.
As of 19:42, the chat appears to be online, but still slightly wobbly. What happened? Was SE a victim of some sort of (new) attack/bug in the chat flag system? Or, was this just a case of a user being over-zealous with flags and the rate-limiter not catching them for whatever reason?
Similarly, why would a chat-flag wave like the one we just saw cause Chat to go crazy in general?