1457
When Baldur's Gate 3 came out, Steam's overall bandwidth consumption went from around 18 Tbps to 146 Tbps
(reddthat.com)
From Steam's self-published stats.
Baldur's Gate 3 could not be preloaded and weighed in at 125 gigabytes on disk, so when the game left Early Access at 11am US Eastern yesterday, Steam's bandwidth utilization shot up 8x over a span of 30 minutes. I know personally, I saw my download hit over 600 Mbps across a 1 Gbps fiber connection.
Kudos to the system engineers at Valve. It is mind-boggling that they have built infrastructure that robust.
I have a friend who worked at a rural ISP serving communities with only a couple hundred residents each. He told me they have a 10Gbit backbone with failover and some customers on gigabit connections, but most are served over DSL/Cable. So 10Gbit x2 over-provisioned maybe 10-20x? I just found those hard numbers for how an ISP is setup very interesting