Epic offered an explanation for why things went wrong in a blog post earlier today, saying a shift in gameplay strategy and an unexpected amount of in-game spectators caused the disappointing experience for both players and viewers.
"While we could pack virtual servers a bit tighter per physical CPU for Playground mode, we still had to use 15 times as many servers as we had been running for the other modes". Now we know, more specifically, that the issue is related to how many matches the Playground mode made versus the Battle Royale mode.
Basically, each node in the matchmaking groups has a list of dedicated, available servers. So much so that it was added and removed on the same day and impacted matchmaking in Battle Royale mode too. "Players that connect to MMS request a server for their region, MMS assigns that player to a node, and the node picks a free server for the requested region from its list", Epic's post reads. The Playground mode is making matches for groups of one to four players at a time. And get this: We've even got a Fortnite Funko release date and, while we'll probably be nearing double digits in terms of in-game seasons by the time they land on our lap, it's at least around the time of the real-life holiday season, one where we're all meant to be jolly.
To fix the problem, Epic says that it split Playground matchmaking into its own service cluster so that its problems wouldn't affect matchmaking for other modes.
The solution was to ensure repeated searches from the nodes for available servers weren't necessary, which meant the team had to bulk up the "rebalance sessions from other nodes". The good news is that the work Epic had to do to bring Playground mode back online will continue to benefit the game as it grows further, and the hope is that we won't see another failure like this again.
We can definitely speculate on what will be released, however.