All they really care about is a way of maintaining a well connected mempool in order to quickly receive any newly broadcast transactions. For each incoming transaction, they will presumably have something like a huge lookup table database
I hadn't realized this until you posted it. It makes sense, and they don't even need the mempool anymore, all they need to check is every new transaction the moment it first arrives. So that's at most 7-ish transactions per second, or better: every xxx milliseconds a new transaction arrives, and they check them one at a time.
Kinda like BitBonkers, but with sweeping instead of visualizing.