I was responsible for a website (one of a many of this kind) that provided access to a niche auction platform. At some point in the beginning of 2010s it became a subject of a precisely coordinated series of timed attacks designed to disrupt bidding of one of our prominent clients in the specific auctions. It was enough to bring down the service for ~5 minutes to prevent the client from winning.
Eventually we migrated behind CF and the problem was solved but I couldn't help but wonder if there are some applications for which even a few seconds disruption (I assume that's the minimum time Cloudflare needs to begin effectively mitigate the attack of this scale) will be disastrous and what could possibly be done in this case?