For some color here, the Fermi estimate for number of unique consequential writes Equifax will make in a day is about ~1 billion and the number of "pull that entire file, please" is in the tens of millions.
All the data is hot data. That's what Equifax exists at all. There are multiple internal services which can cause "pull that entire file." If you lose any of them, your data store doesn't matter; there goes the ball game.
Someone's about to say "But rate limiting!" and not understand that Bank of America can ask for 10 million files at a time. (One cron job talking to a another cron job, etc etc, will fetch an update to a substantial fraction of all of their customers to update their internal records for underwriting. A larger recurring use case is "Refresh the soft pull on everyone in our marketing funnel whose pull is stale." Note that that is a sizable portion of the adult population.)
All the data is hot data. That's what Equifax exists at all. There are multiple internal services which can cause "pull that entire file." If you lose any of them, your data store doesn't matter; there goes the ball game.
Someone's about to say "But rate limiting!" and not understand that Bank of America can ask for 10 million files at a time. (One cron job talking to a another cron job, etc etc, will fetch an update to a substantial fraction of all of their customers to update their internal records for underwriting. A larger recurring use case is "Refresh the soft pull on everyone in our marketing funnel whose pull is stale." Note that that is a sizable portion of the adult population.)