If Valve was looking to stress test its servers for any reason this weekend, running the New Bloom event was a good way to do it. The festival was the latest content update for the MOBA and brought with it a new game mode that allowed players to go up against the Year Beast to try and win unique awards.
This update saw an average of a million concurrent players on the game at almost all times, partially because the new game mode was only available at random times, leaving people queuing for lengthy periods, or hopping on all at once when they saw that the game mode was live.
As well as being significant because it made some of Valve's servers creak and wobble though, this was a major milestone for Steam in general, as DotA 2 became the first game ever to have more than a million people playing at once on the platform. Unfortunately it's clear that Valve will need to do a little more to safeguard against this sort of surge in the future though, as a fair number of players took to Reddit to complain about delays in finding a game, or frequent disconnections.
[Thanks PCG]