In the first place, if you see a developer write a blog that exceeds 2,000 words you know the shit has really hit the nail on the head D2R Items. This is a huge explanation of all the problems that are facing Diablo 2: Resurrected players currently, and is so large because the problems do not stem from one problem but are a result of a variety of issues, which range from an inability to deal with the popular game's reputation, its structure, and even down to the possibility that players are way more efficient at smashing Diablo into the dust in 2021.
The first major problem outlined by the team concerns how players' identities and their data are stored. If you've played an Activision or Blizzard multiplayer game over the past decade then you'll have noticed that you generally login to several servers that are that are as close to your current location as is humanly feasible. It's not a specific server per se, but the cluster of servers which serve a whole region.
Anyway, these servers all have their own databases for each region that hold the data of the characters playing on them. This is required because there's an inordinate amount of players taking part in Diablo 2 to just continually upload all of their data to a single central point.
"Most activities in games occur on this regional database because it's faster, and your character is locked there to ensure the character's record's integrity. The global database also comes with an emergency backup in the event that the main fails,"These regional databases will periodically transmit informations back over to the central database which means that Blizzard is able to keep a single record (with backups) of your Thicc Level 88 Barbarians, Necromancers and the like cheap D2R ladder items. Which sounds all well and great until the central database becomes overwhelmed and the entire system, along with the engineers that work in it, demands time off.